I guess if you post in the GS4 forum you'll get different answer to posting in the One forum. I'm used to Touchwiz so I like it, but it comes with a lot of Samsung apps that remind you you're on a Samsung device (like "look at me! I'm here!"). Sense is more of a stock android platform that runs in the background so you don't notice it, and some would say that's better for their needs.
Of course, there will be a million roms out there to change the platform to whatever you like. You should really ignore any Sense vs Touchwiz discussion and focus on things you can't change, like the hardware. Compared with iOS, you'll love either one to bits, simply because they are far superior to iOS in terms of functionality and customisation capability.
HTC One doesn't have expandable memory, you can't easily take out the battery, and it has a smaller screen. Those reasons, and the fact I like some of Samsung's gimmicks, are why I chose the SGS4. If you prefer something a bit more compact and without many additional features, the One is probably more suited; it also feels like a more solidly built device than the plastic SGS4, but that just increases the weight (by 12g
Another focus of discussion is NFC. SGS4 has it whereas the One does not. Some people feel that NFC is a security risk, and others find it useful. The SGS4 allows you to turn NFC off if you like, so it shouldn't be used to sway a decision.
In general, reviews are better for the One, but that's because it came out first (just). Also remember that the reviews are based on the stock firmware, so a lot of pros and cons come from the Touchwiz vs Sense debate.
So in summary, I would suggest the SGS4, but that's because I have one