As someone who played Warcraft 2 and League of Legends before ever playing a DOTA game, I have to say that DOTA2 is practically unplayable to me. To better define this, there are things that work a certain way in League of Legends (such as auto attacking), that are so hard to manage in DOTA2 that I could not stand to play the game.
There are other severe differences that makes the game more... boring from a player perspective. Certain guys have abilities that use up almost all their mana. It makes you wonder why you would ever use a rank 1 Q ability if its not meant to be used more than once. The camera lags a bit, so that moving the camera while moving away quickly results in the camera NOT moving fast enough and the character turning around to auto attack.
Secondly, the character names are really boring for so many of them. Its more like you are picking a class rather than a character to play. I would rather be choosing more of a character, the way Street Fighter is more about choosing the fighter than the Shotoken Karate guy.
This is not a game you check out if you started with League of Legends. It is a game you play if you loved DOTA and though League of Legends was too mainstream. DOTA2 focuses its gameplay towards the hardcore player. As such, I don't see them equaling the numbers that League of Legends has reached.
Has anybody else played DOTA2 and League of Legends? Was your experience different?