Not asking which is "better". I'm curious which of the two games you primarily play and why? Care to get a discussion going here? I feel like mobile MOBAs are going to really start taking off so I'm going to pour some time into them, but I'd rather focus on only one of them
I prefer Vainglory. You level up while in a match. There are item upgrades to buy in match. It's a full blown moba for your smart phone/tablet. Call of Champions is a super streamlined moba. No leveling up while in match. No items to buy at all. CoC has fast queue times (10-30 seconds). Vainglory has about a minute queue. Matches in Vainglory typically last 15-30 minutes. Matches in CoC are a maximum of 5 minutes. When I tried CoC the matches are over so fast I felt like I never had a chance to understand what was going on. So yeah Vainglory > Call of Champions by a landslide. I will say that if you're going to play Vainglory it is advantageous to play on a tablet if possible. It's still playable on a phone but I always felt like I was at a disadvantage when I'd play on my iPhone 6 instead of playing on my iPad Air.
I'll be using an iPhone 6. Hopefully that'll be enough to handle the game. Vainglory seems really good and I see it on Mobcrush daily. Doesn't seem TOO greedy for cash either, which is always nice.
It can definitely handle the game. I just found it harder to tap on mobs and heroes I'm trying to kill
Oh and you definitely don't need to spend money on it. If you play enough you can probably get like 1 new hero every month or so. I started playing in early December and have like 13 heroes I think. Although I have spent $30. Used that to get Kestrel, Reim (whose horrible), and like 1-2 other heroes. The rest were bought with currency earned from playing.
This is the game I play the most. Even more so than my PS3, Wii U, or 3DS games. If I could afford it I would buy an iPad Pro just for this game. It's that good.