Im using XDK for my first game. Im getting really good performance on Android and iOS. I get 60fps on my old test devices: iPhone5 and Nexus5.
Im just discovering that plugins, like everyone says, are a complete pain in the ***** but ive just managed to get Chartboost interstitial ads and Google Analytics working in XDK using the cranberrygames plugins... how long they continue to work remains to be seen.
I tried my game on cocoon a while back just to compare, and performance was good on that too. But there was a bunch of stuff broken with the game, I guess because I had been testing on XDK right from the beginning. If I had tested on cocoon from the start too, I would have picked up those bugs of course.
I noticed a couple of C2 games published recently on Android were built in Cocoon (Lunar Mission and Artillerists), so those devs are obviously happy with Cocoon.
One thing I dont like about cocoon is their logo being slapped at the beginning of your game. But thats a minor thing. Im happy with XDK provided ads and analytics continue to work