I got wondering this some time ago.
Ended up buying a few.
Sony Z4 and Galaxy Tab S2 by far beat everything else hands down.
I may be wrong, but I am only going by what I own of course, and I have asked around too.
For me, the S2 edges out, but then I am a Samsung lover, as I also own a 10" Pro, 7" Tab 3 a Note 3 as my main Phone.
I have a stupidly large collection of others, but they are really only used for going out so I dont risk losing or breaking my Samsung or Sony cos they aint cheap.
Interestingly, I saw a 10" Prestigio in shaftlins and it must be end of stock cos it was on the counter for silly cheap and so I grabbed it purely for a giggle and for the price, its a brilliant tablet. Its nowhere near the speeds of the better end, but its no slouch either and it has a great crisp display and I am very impressed with it. I have also bought an 8" prestigio purely because the 10" was great but that is possibly the most useless one I have ever bought, bar one of the cheapie ones from the bay of course.
Another nice display is the Asus Memo. It chuggs along nicely but again, its not going to beat any speed records, but it does look nice.