I hope this is some horrible joke, but let me make some things clear as someone who has played nearly every MOBA on the market:
DotA2 is a sequel to DotA: Allstars, the Custom Game Map from Warcraft III developed by a guy named Icefrog. Icefrog was hired by Valve a couple years back to make a MOBA for them (DotA2). An earlier version of DotA was developed by a couple of guys with the alias' Guinsoo and Eul, but it wasn't nearly as popular or refined. These 2 guys helped found Riot Games and develop LoL some years later. So the people at Riot Games developed a version of DotA, and Icefrog took over when they went on to form Riot Games, and with his changes and focus on balance and refinement, the popularity of DotA (and by proxy--MOBA's) exploded. If it weren't for Icefrog and DotA: Allstars, Riot Games would have never gotten funding to really start developing League of Legends.
Now that the History lesson is out of the way, it's important to recognize the difference in the philosophy of each game. LoL focuses more on rewarding people for playing well, but not penalizing them in anyway for playing badly/irresponsibley. DotA2, rewards people for playing well, and punishes them for their mistakes, and their teamates mistakes. In LoL when you die, you aren't really losing anything, but in DotA2 when you die, you lose gold, your opponent gains gold, and you lose tons of time in the lane which they can use to push through a tower and possibly give their team a big edge.
Even more than the dynamics of dying, the way creeps are handled is vastly different. In LoL you can last hit enemy creeps to get extra gold. In DotA2 you can last hit enemy creeps for extra gold, as well as being able to last hit your own creeps to prevent the enemy from getting extra gold (and experience). This almost Meta-Game allows for a lot more depth to the game, and a huge increase in the learning curve of the game, because even if you know how to play every hero flawlessly, you're screwed if your opponent prevents you from last hitting a single creep.
As for character balance, LoL has been out in one form or another for like 5 years at this point, it has had a lot of time to add characters here and there, as well as balancing pre-existing characters. DotA2 is still in Beta, and is in the process of adding more characters from the actual DotA roster (which is at something like 80-100 heroes) to fill in gaps. By the time DotA2 goes live I expect it will have at least 60 heroes, and be very well balanced. One thing that makes balance automatically better than LoL, is that everyone has access to all the heroes in the pool, all the time. There's no advantage to players who spend more money or time on the game, because a lot of the heroes outside of the pool are substantially better than the ones in the pool at any given time.
Overall I think DotA2 is a better game than LoL, but then again, I think HoN is a better game than LoL. Everytime I play LoL I always end up carrying the team with a hero that everyone says is bad and incapable of doing so (Cho'Gath represent). With DotA2 the game is a lot more difficult because of a lot of elements that LoL has just flat out removed over the years, leading to a simpler less dynamic game.
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