I played HoN the last few days. Thus far, I'm unimpressed. It looks beautiful, I'll give it that. But it feels like a face-lifted dota, that you have to spend about 30 minutes figuring out which hero and what item is it's dota-equiv. Not to say it's a bad game. If you were content with Regular DOTA, then the next logical step is HoN.
I feel LoL is a lot bolder. Completely different and new items, as well as completely new heroes. There are some heroes in LoL that are inspired by dota heroes. But HoN has carbon copied their heroes from DOTA.
Also, the match-making. People complain about the LoL grind, but at least it's a lot better than the Warcraft 3 game list where host will kick you for no reason before the game starts.
Not to mention, the summoner spells, mastery customizations, and soon to be runes. AND ITS FREE. Yeah, LoL has some grind to it, but I don't mind that since, actually playing the game itself is fun.
I know, the meta-game of LoL is currently in the crapper, but that's something a few patches will remedy. overall, I'm more impressed with LoL's direction than HoN's. HoN doesn't have much meta-game issues, because it isn't really a new game - just kind of a face lift of an already existing one.