It doesn't look pretty sony's skin/UI IMO but it does the job. Has a nice enough unified feel throughout and the stock apps are good enough, besides it is for the best that they didn't use any/much black due to the poor black levels
Touchwiz is closer to stock android for the MT window and some other things, however, almost everything else about it is awful imo, the colour scheme and apps I can't stand, no unified feel throughout, cartoonish colour scheme, disorganised apps but it has the best implemented features i.e. smart stay, smart alert, smart rotate, multi-view (granted you can get the majority of these as apps now though). However, if you root you can flash a stock android theme i.e. JB domination as kona said, which improves it a lot! AFAIK there isn't anything similar for sony phones, with HTC, there is a similar theme for the one X but not quite as good and unfortunately there is nothing for the one S
I love sense V4, the only things I hate about it, are; new battery graph in V4+, white colour scheme. The stand out features for me compared to other skins is that it has the best unified feel throughout, apps are nice looking and functional and the camera app is the the best overall as well as the browser (text reflow is what makes it so good combined with improved quick ICS controls and flash, also find it to be the fastest and smoothest browser) The multi-tasking window is poor, but functional enough I find, from photos/screenshots it looks like you have to slide to the app you want in order to select but you don't, can just tap either of the 3 shown on screen and it switches to whatever you chose.
Motorola's new skin is very good, without a doubt the closest to stock android, have a few neat features implemented (not to the same level as Samsung, HTC though) and again, has a very good unified feel throughout. Also, use mostly a black colour scheme, which is a huge plus for SAMOLED screens.
Stock android is great, best theme/colour scheme without a doubt and also has a somewhat unified feel, not to the same level as sense and motorola's skin though. The apps look nice but are very limited compared to other skins apps especially the camera. Shame they dropped the stock browser for chrome
Not that it really matters too much anyway as being android you can do whatever you want
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i.e. stock android without having to root etc.
Might as well post this in here too.
Want to try and achieve a stock android look (mostly), however, without rooting?
well this is how
stock android keyboard
stock Alarm clock
Stock SMS app
Dialer with this
theme
Stock calendar
stock Gallery
Stock camera
Nova launcher prime with the built in stock android icons
Lock screen (can get the stock lock screen theme/UI)
Stock (CM10) calculator
Then there are apps to replace the notification bar i.e.
omega,
status bar +,
super status bar, however, they are a bit buggy!
And everything to do with sense, touchwiz is either disabled or hidden via nova
The only things that you would see on my one s currently, which are sense related are; the camera, gallery, notification bar, multi-tasking window, browser and settings menu.