You will sit lower on the bike, you will lose the ease of spinning a smaller crank will give you. You will have readjust the way you sit on the bike (more towards the rear).
For your height maybe you should try it first on someone's bike before you consider doing so. I'm 5'8" and I did convert from a 170 to a 172.5 and do like it, but I do notice the lost of a little ease of spinning, yet on the hills I gain a more satisfactory comfort for climbing with the larger crank. So it's a give and take thing.