Overall UI and screens
Got to say, I like the Win tiles best. There's the list of applications, and there's the tiles. And I can add more than just apps as tiles. The tile can be a contact person, the live tile showing the person's picture and latest social media updates. It can be a specific "page" or folder or part in an app. Some tiles are live, others not. What I do miss a bit on the WinPhone, is the multiple screens, like Galaxy Tab and iPad have.
On Android, I can add shortcut icons to both applications and parts of applications, and then there's the widgets that I like, too. And I can arrange and drag and drop the icons on each screen page as I wish. On iPad, the icons are apps only, and always auto-organized. But then again, I could, if I would like to, group them inside folders. But no live nothing.
The Galaxy Tab, or rather Android, has the functionally best keyboard, in my opinion. I really like the smart possibility to press and hold in order to type special characters and numbers. And the possibility to not use it, for of course it also has the toggle button for the special characters keyboard, just like iPad and Lumia the Winphone that both lack the press abd hold feature.
As for the iPad, I personally like the split keyboard (came with iOs5), even though the layout isn't perfect in all applications, causing the keyboard to float on top of the field instead of below it. But the best feature in iPad is the possibility to connect the nice small and lightweight wireless Apple keyboard to it, is a definite advantage. How much easier would it be for me too now to be typing this with such a keyboard than typ(o)ing on this touch kb.
Here too, the feature most to my liking is on Galaxy Tab, i.e. Android. First of all, it is possible to simply tap the cursor in the middle of a word, and then select the whole word if needed, or move the cursor to a different spot by dragging a tool.
I don't really like it that by tapping I can place the cursor only at the end or beginning of a word, even though I finally am starting to get used to the press and hold and then place the cursor way of doing it. The select with a double tap is nice though.
With my Lumia, I love it that I can combine several Outlook accounts into one list view. Of course I could add even the gmail to the same list, but I like to keep the private and work emails separated. And let's emphasize: I like the list view, also on the Androids.
That as opposite to the UI of the iOs email client, that combines all email accounts to the same app without asking, and the list view isn't even the main view (at least not on iPad), but a side bar. I sincerely don't like it that the app opens to an email, the last one I read, instead of showing the email list of a selected mail folder!
Same goes for the OneNote app (and actually also Dropbox app and some other similar ones too) for iPad. Otherwise it serves its purpose well enough; I can easily access my cloud shared OneNote notebooks, add notes and such. But, for obvious reasons, the OneNote client for WinPhone is better.
Battery charge level display
The iPad, the iOs, has it natively, the battery charge level percentage is always displayed by the battery. For the Android, you can get a free app to add the percentage display in the status bar. For WinPhone, there apparently is no way to even build such an app. When I want to check the exact battery life time, I need to go to the setting - but at least it's there.