First, I should mention that I'm still unsure about my choice and therefore my justification will probably be pretty unconvincing/incoherent. Nevertheless, I'll take a stab at trying to explain my decision. It's also worth nothing that I don't think any of those three choices are particularly bad in this situation, and my choice was largely based on preference.
$$Bm21
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . 0 . . . |
$$ | . . . . . X . . . . . . . . a b c . . |
$$ | . . . O . . . . . X . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X . . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bm21
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . 0 . . . |
$$ | . . . . . X . . . . . . . . a b c . . |
$$ | . . . O . . . . . X . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X . . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
So, my first instinct was that either a (because it completes an outside) or b (take corner and chase white a bit). I then thought a made more sense because it seems more reasonable given the board state (makes no sense for me to try to chase white when my top is not that that develop-able - for example, I wasn't that happy with below (though it may just be my bad judgement):
$$Bm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . 2 O 3 . . |
$$ | . . . . . X . . . . 4 . . . . 1 . . . |
$$ | . . . O . . . . . X . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . a . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X . . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . 2 O 3 . . |
$$ | . . . . . X . . . . 4 . . . . 1 . . . |
$$ | . . . O . . . . . X . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . a . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X . . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
One more issue with above is that there are weaknesses around a that remains.
So, my preference then was to seal white inside. But then I was sort of unhappy to give up the corner for relatively uncertain potential outside (since my right side is on third-line and white is quite solid almost everywhere).
The main issue was that I could not find a way to seal in sente, for example:
$$Bm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . 2 O . . . |
$$ | . . . . . X . a . . . . 3 . 1 8 . . . |
$$ | . . . O . . . . . X . . . . 9 X 4 6 . |
$$ | . . . . . . . . . . . . . . . . 5 . . |
$$ | . . O . . . . . . . . . . . . 7 . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . b . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X c . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . 2 O . . . |
$$ | . . . . . X . a . . . . 3 . 1 8 . . . |
$$ | . . . O . . . . . X . . . . 9 X 4 6 . |
$$ | . . . . . . . . . . . . . . . . 5 . . |
$$ | . . O . . . . . . . . . . . . 7 . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . b . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X c . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Then there are a lot of nice points for white (a, b, c only a subset).
Looking at it now, I'm not that would have been bad, but I really wanted some points to not have so much pressure to take a big centre. In addition, I also thought that the 3rd line stones on the right side makes taking corner and driving white out more attractive.
Another possibility is below, which will likely end in sente for me, but I didn't like the cuts it left after white lives in corner (though again, looking at it now, it doesn't seem too bad).
$$Bm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . 2 O . . . |
$$ | . . . . . X . . . . . . . 3 . 1 . . . |
$$ | . . . O . . . . . X . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X . . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Bm1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . 2 O . . . |
$$ | . . . . . X . . . . . . . 3 . 1 . . . |
$$ | . . . O . . . . . X . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . O X X . . . . , . . . . . O . . . |
$$ | . . O X . O . . . . X . . X . . O . . |
$$ | . . O O X . . . . . . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
So I once again came back to the idea of taking corner and forcing white outside. My main concern, then, is on how I should try to end up in a better position on the top side (since it's sort of open). I thought the bump helped white a bit by giving an extra extension on the second line and therefore a bit wider extension on the top. Additionally, I wasn't as concerned about the top right weakness again because I'm likely to get another move to protect.
I don't know how accurate my assessments were and whether I've expressed my pretty fragmented thoughts coherently enough. Let me know if you would like any clarifications or have questions
