I used the tab s 8.4 for 3 weeks, I didn't like at all the small lags here and there, expecially while browsing.
I returned it and I got a tab pro 10.1 lte (snapdragon then). It's not perfect yet, but much more enjoyable (I've been using an I pad air for 9 months).
Well, of course the screen of the tab s was incredible, but to me it's the whole experience that matters, this means performance and smoothness too of course.

Just my two cents