IMHO Stock jellybean >>>>>> wp8 and iOS. Android also has the best browsers (chrome >>>>> safari and super shitty ie. Dolphin beta >>>>>>> safari and shitty ie. Opera mobile >>>>>> safari and shitty ie ect.) It offers the most customization (although stock jellybean is by far the best looking mobile os is IMO.)
Edit: on android you also aren't tied to any stupid syncing software.
I can't understand how you could think Safari is shitty. Have you used it? Grab an iPhone/iPad and put it next to GNex/Nexus 7 Chrome. Safari is absolutely more responsive in scrolling, zooming, and rendering. Android browsers have a come a long way but they're still not as fluid and 1:1 responsive; though they're very good. You could argue that the features of Chrome are better, but I still don't think Safari is shitty even in that comparison.
Edit: FUD. iOS hasn't been tied to iTunes in a while now. My parents have an iPad that has never synced or connected to a PC.
What syncing software does WP8 use? Honest question.