In general, the solid connection (c18) is better than hanging connection (b18) because it doesn’t leave the same ko threats on the board.
B18 is better at creating eyeshape, so it can better if your group isn’t guarantee to have 2 eyes with the solid connection. But if you know that your group is well alive even without making extra eyespace, there isn’t usually any good reason for allowing white to have those ko threats at c18 and b19
C17 is a bit “funny” shape, but it works in that pic as well. Note that it alse leaves ko threat behind (peep at b18 or the atari at b19), so ~only situation where c17 is stronger than c18 is if you want to block the corner from the direction of c15 stones. It might make sense if c15/d15 stones would have been white here, but since they are black there isn’t any good reason for it.
So yes, all of b18, c18, and c17 would work here, the subtle difference is mostly ko threats left behind since that black group is alive.