I'm trying to decide between those two phones as well. I'm on an LG optimus S right now so either will feel like an upgrade by leaps and bounds. I love the One's low-light performance (I'm THAT person who just HAS to instagram when she's at a concert or show) and I'm ok with installing apps to get a launcher. with sprint, I wait 2 years to upgrade my phone, and the ability to change out the battery on the S4 down the line is appealing. I'm not sure which would provide the best update support over the next two years; I'm assuming being able to root would play in the most with getting the latest android build in a year, year and a half, but that's based off my experience with sprint and the optimus S. I use app2sd a lot on my current phone, but its in-phone storage is dismal, so it may not be an issue with the One. I doubt either of these phones will fit easily fit in my pockets or running belt (I use runkeeper and charitymiles on outdoor runs), but since the One is a little smaller, it may squeeze in them a bit better? and as a commuter student, battery life is a biggie, but that seems pretty subjective.
what may be make it or break it for me, besides the is 3g performance--sprint STILL doesn't have 4g LTE in Denver. I'm hoping they'll get their act together in the time I'd be using either of these phones, but if that's not anytime soon, can anyone speak as to how they'd perform in 3G?