Hopefully this answer is not too outdated. I've tried both of the Galaxy S4 and HTC One for 2 weeks and decided to stick with HTC One.
The only advantage of Samsung model is the wide availability of accessories. Also is the removable battery and SD card.
While the HTC has better:
- Speaker sound
- More accurate and detailed screen
- Better camera in low light; also super wide angle front camera
- Earbuds in the box were unbranded Beats, great sound!
- Solid body and sleek design (subjective)
- Beautiful software (subjective)
I think I'm gonna write an article about this :)