I prefer Pokerstars for mobile play. It's the most stable app for me and i like the classic table design on stars better than the style that 888 and GG uses. The GG app is a bit overloaded. And i can't find the cardschat tourneys on the app. The filters don't seem to work well in the app.
"Love thy neighbor as thy self" -Kurt Cobain
I can not compare as i have only worked with pokerstars android app (it is one of the few licensed operators in my country) but stars is working great for me. Good graphics, moderate battery usage and good features. I would be happy if some more advanced features from PC version were available like saving hand histories or the ability to enter star codes and change table themes but even now i am quite happy with it.