Just got my HTC One 2 Days ago and IMMEDIATELY flashed the 4.3 GPE Stock ROM.
It's all based on personal preference, so I will give you my thoughts.
AOSP feels so much snappier to me and I really like being able to fully customize any and all aspects of my phone with out Manufacturer skins getting in the way. I had and S3 and touchwiz was absolutely abysmal. It lagged, and the interface looked very ugly to me. Sense 5 looks great, don't get me wrong, but I don't like all the HTC and Carrier bloatware clogging up my phone and hogging resources that could be best used for keeping my interface lag free. Granted, 4.3 GPE ROMs for the HTC One don't have that many mods and things available to them yet (I tried getting MoDaCo to work but I couldn't, same with the Xposed Framework) but in no time I am sure that 4.3 GPE will have all the mods and themes available to them that 4.2.2 and lower have. (You could make the argument that there are custom ROMs with baked in features, but I prefer as much a stock experience as possible with a few mods in place.)
tl;dr AOSP is faster imho. It looks prettier too and allows me to fully customize any and all aspects of the device without manufacturer skins getting in the way.