Hmm, I'm not going to say much about game mechanics, most everyone has gone over those things to death, this and that, this is deep, that's not deep, complexity lack of complexity, and those are all valid points. Dota 2 may very well be the better game, it might have better mechanics, more balance, or whatever the hell have you, but I still prefer my LoL.
Why do I do this?
Lore, world, setting, and all that, those mean a lot to me. I love League of Legends to death, it's fun to play, the champions are varied, and despite the "rigid roles" that champions are supposed to fit into, I'll often try really weird things, not even caring if I lose, and there are rather flexible champions. (Kayle for instance) but it's all overshadowed by the world, lore, and characters. I've looked up the heroes for Dota 2, read their lore, and their names and it's all rather short, it's rather...boring. The lore is a bit interesting but it doesn't have as much detail and effort put into it as League of Legends does. There's not as much interesting play going on as the trinity hate force of Urgot, Garen, and Jarvan the IV. There's nothing quite like Mordekaiser's (Huehuehue) heavy metal band Pentakill. There are characters with relationships not outright stated but implied by their lore. For instance Brand and Olaf don't really know each other, but they're from the same place, and what about that new champion Nami? She just so happens to be searching for a moonstone, which hasn't been brought to the meeting place for the first time in forever, and there just so happens to be a champion of the moon prancing about the fields of justice?
I've done a lot of reading up on the various Dota 2 champions, er, heroes, and overall I'm not impressed. They're not completely boring or entirely unoriginal, but their lore is more there just for the sake of having some kind of story. It seems to me, like the effort of just someone going, "Meh, might as well give them some kind of story." While in LoL you have entire cultures being drawn up with characters from each, whether it be the duo of Pantheon and Leona, the former a picture perfect representation of his people and the latter being very rebellious but somehow blessed by the sun they revere. To me LoL just has more interesting characters, sexualized or no.
Then there's the world. Now, I've been able to find out only a little about Dota 2's world lore, and to be fair it was actually pretty interesting. There may be a hell of a lot more regarding it that I haven't found besides the comic and story of the mad moon that makes it a lot richer and provides more details. However, I doubt it can compare to the city states of Valoran, the distant continents that might exist, the impact of the rune wars and the effects they've had on the champions (Like Zilean's chronowhatever) and the alternate worlds the summoners have drawn champions from in an effort to make the League viable so as to save their world from the sure destruction that would come from another terrible rune war between what would almost certainly be Noxus and Demacia...
Not to mention the threats posed by both the Shadow Isles and the terrible nightmares of the Void. While Dota 2 does seem to be a pretty straightforward thing between Radiant and Dire.
So to try and wrap up, my main reason for liking LoL over Dota isn't anything gameplay wise. They're both sound, they're both solid, they've both got their pros and cons. No, my reason for choosing LoL over Dota is the story, the characters, the world, and all those other things. So far...I'm pretty much the only person to mention this...that's probably because I'm wrong though.