I have compared the 2 phones for hours on the web.
the gs4 has hands down better hardware guts and it does not use on screen keys to take up real estate and also has a removable battery and an sd slot.
lets not forget that its a 4mp vs 13 mp camera also.
I am planning a trip to vegas soon and will bring an extra battery with me so I don't have to worry about the phone dying on me either,these are all my reasons for picking the gs4 over the htc one and I am sure others are in my same boat also.
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Well if its anything like the gs3 I am sold sight unseen as I have been suffering working with others at my work that use that phone and pretty much saw first hand what Iv been missing out on for the last 3-4 months.
It looks like a slightly bigger version of the gs3 and I am sold on it!!!
Its actually a bit smaller/slimmer