Just to sort a few facts out :
There has always been only one main person that is working on DotA, but yes Guinsoo is now working for Riot which had created League of Legends. Guinso was the initiator of DotA Allstars, but he had stopped working on DotA in about 2008 I think.
But DotA 2.0 is being created by Valve and Icefrog who is currently working on DotA. DotA 2 will be DotA just with a better engine and better graphics. In my opinion LoL simply is a different system that e.g. has these summoners which most likely will not be a part of DotA 2.0. Therefore I do not think that LoL will have as much concurrence as Heroes of Newerth will have.
By the way I do play both, LoL and DotA and I would also play HoN if you didn't have to pay for it. So you can choose both and don't need to stick to one.
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