Originally Posted by
unterhausen
I would get the 54. You can add more spacers unless they unwisely cut the steerer.
This^^^
Adding spacers does not affect the steering/handling, unlike shorting a stem too much can. Further, if the OP is looking for a more upright position, they might end up needing to shorten the stem even on the 54.
I am someone who needs a more upright (higher stack to reach ratio) than most, and the best results I get are from going with the bike with the best reach (the smaller size) and using spacers to increase the stack.