To put it simply, League is a watered down version of Dota 2. There's not as much depth to the mechanics nor variety of gameplay. In Dota 2, often times heroes are blamed as being overpowered and their skills accomplish giant things and can sometimes have global effects, but in my opinion, this simply adds depth to the game. Heroes (or champions if you come from LoL) are supposed to be overpowered so that they their powers can be used in creative ways! I want to be able to accomplish huge things in fights! If you guys want to call that unbalanced, suit yourself and play League, where many skills just start to get watered down and resemble each other.
League is a game where some champions you have to pay to unlock or play enough games to unlock. In Dota 2, all the heroes are unlocked from the start to assure complete freedom to learn. And Valve just flat out cares more for its community than Riot, a company known to be greedy for money and popularity. In fact, Riot's been rumored to pay off MLG to not include Dota in its E-sports venue. Dota is truly a players game (the players have already contributed half a million dollars to the International Dota 2 championships prize pool) and I for one am proud to be a Dota 2 player.