Both use ELO system for online gaming matchmking. But one is vastly superior.
League of Legends matchmaking simply cannot be balanced around ELO because of 8 other variables in the game. I believe we will start to see a large drift from LoL / HoN within the coming weeks as people realize that their arbitrary system for matchmaking repeatedly yields poor results.
The only way to fix this in DotA was by using third party software to banlist people or private servers with level requirements and integrated account baning. LoL could learn a thing or two.