Default [Q] Why is this tablet's WIFI so poor?

I have this tablet, a samsung galaxy s4 and my girlfriend had an ipad 4.

Basically, compared to my s4 and the ipad 4, webpages all load slower, when i update apps via google play store, they update a lot slower than my s4 updates them, also i play clash of clans, no matter wyhere i am in the flat with my s4 or my girlfriends ipad i never loose a connection to the game, on my tablet i regularly loose connection with the clash of clans server and it will restart and i may loose the odd game because it lost connection half way through a battle etc..

This is all using the same wifi at the same distances etc..

I have turned off wifi optimisation as this made the wifi even worse on my tablet, even though the name suggests that it should make it better lol

Any ideas, or is this trablets wifi just not as good?

James
Samsung Galaxy S4 I9505
Sony Xperia Z2 Tablet