S4/One first impressions - help sought!

Hello all!
Long time lurker here, decided to finally make a post regarding the mentioned phones. I've longed for an upgrade for a while and my iPhone 4S isn't cutting it anymore. I seek something different. Today I finally got a chance to play around with the S4 and the HTC One. It didn't really make my choice any clearer, thus I seek some advice from seasoned One/S4 users.


Hardware

S4 - It was surprisingly light and surprisingly, felt fairly good in my hand. It was very comfortable to navigate on the screen despite its grotesquely large size. The plastic was a huge turn off though after toying with the One.

HTC One - Heavy, stunning and gorgeous. A magnificent bezel, reminded me a lot of my first smartphone (iPhone 2g). Somehow, it felt bigger and clumsier than the S4. Am I imagining things here, or is it actually larger than the S4? My thumb struggled a bit reaching the top of the screen and the buttons, in contrast I didn't experience any of this on the S4. Does one get used to the weight? I was actually fairly concerned about it, the S4 was easier to handle. Any rule of thumbs on how to use the device?

Software

S4 - I adorethe screen and launcher actually. Feels fluid, rapid and the screen is brighter than a thousand suns! Some features seemed also pretty darn useful, whilst others felt a bit ''gimmicky''. Opening the mail app, phonebook or messages made me cry a bit on the inside. It looks incredibly...well, childish? Rushed? Colors are everywhere and it makes the phone seem cheaper than it really is. Very fast UI though! No delay whatsoever. Other then that; touchwiz makes baby Jesus cry.

Htc One - The hell is up with the launcher and navigation buttons? How do I change the wallpaper? Do I really have to go into settings in order to do this? On the S4 you just long press the screen to get these options. Can one enable quick toggles in the notification window like the S4 has?
The navigation buttons confused me as well. The S4 worked similar to my sisters N4 and a colleagues S3, the HTC confused me. I didn't get any feedback from pressing them and wasn't always sure what would happen when I pressed the ''home'' icon. Multitasking - wtf? Feels ''slow'' compared to the S4 and N4.

The screen isn't the brightest as well. After using the S4 for a bit I would venture into the Ones settings and try to increase its screen brightness, only to notice it's actually maxed already.

All isn't bad though, phonebook, sms, settings et cetera are incredibly consistent, I adore it actually. x1000 more than touchwiz and stock android, the flat look of sense 5 is mindboggling. The phone feels rather empty though compared to the feature packed S4.
Can one get feedback from the keyboard? I really liked that the S4 reacted (vibrated) when I pressed a letter..

I don't really know what I expect in terms of comments here, but I just felt like writing down my first impressions of the devices somewhere. What does the community think? If anyone has anything to add about what I brought up, please comment! I can't decide on what to upgrade (both are priced at around 850$ in my country)