Vainglory is vainglory and CoC is CoC, they aren't same just because they are fall under MOBA zonar and both for iOS & Android. I have not play Vainglory though but let me tell you the concept of both.

The concept of CoC is optimized for mobile devices and casual gamers, mobile gaming is itself a casual gaming platform if we consider the most, it's like you have school but before that you got 10 mins to play you probably would not choose a game where you need strong attention rather a casual game and something you can finish quickly not only that it takes much more less time to understand the game itself.