Let us know how it is going with your decision!
I know you are torn and really like both phones.
Yep. Currently its like this (these are my subjective personal opinions)
S4
+ Fantastic camera
+ fast in applications
+ unbranded & sim-free meaning updates should come fast
+ I like the design of the phone, it's plastic but certainly not cheap - but do undserstand when folks say it doesn't look 'as' premium.
- Touchwiz is honestly a mess. I'm a graphic designer & illustrator so aesthetics are important to me and the GUI consistency on the S4 is simply appalling. (notification bar only transparent if you use Samsung's wallpaper, repeated applications such as 2 music application, 2 stores, 2 video apps, widgets that dont compliment each other, they look jarring against each other)
- Features such as Air View and Smart Scroll that add little to the user experience and in many ways detract from it.
- Aggressive memory usage, and stuttering in the OS
- Battery life despite having 300mAH more is lasting less time than the HTC One. I'm ending the day on 15-20%
- 9gb storage available is paltry, and with 4.1+ not supporting apps on the SD card it is a concern over storage of bigger software titles in the future.
HTC One
+ Beautiful handset
+ Fantastic speakers (Boomsound) and sound generally on the device with beats making noticeable difference when enabled
+ GUI consistency is excellent - every stock app it has compliments each other
+ Music app is one of the best out there, Beats audio enhances this.
+ FM Radio
+ Battery life was very good for me indeed. I'd get through my day with 50% left on most days.
+ Blinkfeed is great for mobile viewing, and shows great potential
+ HTC Share and HTC Zoe's are fantastic
- Camera 4mp is not the greatest in daylight landscape shots where detail is in the distance, not in the immediate vicinity.
- Aluminium scratches easier
- menu button not mapped to long press of the back button yet - though it should be (even tells you in the instructions)
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The decision boils down to 'does a much superior camera outweigh all the other plusses and minuses of both devices.