The three white stones in the lower-left are pretty flexible; White has f3 at their disposal or the B3 - B2 - E2 sequence. Therefore I think that an extention to the left and a follow-up against the corner are Miai to help these stones settle. Also the fact that black played low at C12 makes a move on the left less valuable for both.
I would suggest R17 here. The corner territory is important for points and the safety of white’s and black’s position.
An approach to the lower-right corner also seems good to me. In this case I would probably choose the high approach at Q5, because the right-side is somewhat “flat” due to the situation in the top-right.
R17 would greatly strengthen White’s upper side. Q5 would get us into the lower right quadrant, which I also think is important. When I played through all the AlphaGo Master games back in 2017, I was impressed by how it seemed to prioritize having an early presence in all quadrants. I don’t know which of these moves is better, so I will vote for whichever one gets the most votes.
Yeah I do agree that C10 will leave a weakness which will awake as soon as black group is strong enough. Now I feel C9 to be too mild on black so I join ideas that it’s all a bit slow on the left. I switched to the right side, approaching the last corner (usually the priority).
My immediate thought would be to either extend on the left or approach the bottom right. However, I really like the result from the joseki @mark5000 suggested. I never would have thought of that one myself.
I put some variation on that joseki in the game demo.
Well seems to me that it’s hard for black to get any better result. So I am convinced it’s a pretty choice.
I’m also guessing that however this upper-right-corner joseki turns out, Black will need to omit the final gote move in the sequence to prevent White’s large extension at the top
