Don't make a tire size decision based on standover height. The bigger (taller/wider) tire will be heavier, but hopefully able to run lower pressures, therefore more comfortable, and able to roll through the rough stuff. I pulled all the 23s off all my bikes. I run 25 on my two "fast" bikes, 28 on my touring (the biggest I could fit on the rims, btw) and 32 on my singlespeed. The 32's feel the best for bombing around town, going off-road, etc.