I quite enjoy both. However, hon is a lot more fast paced than dota and just feels more graphically better. But on the downside the community is just horrible and there is a huge lack of teamwork in the mid 1400-1600mmrs.
Dota 2 however, is a lot more slower paced, but the community is outright better. On top of that, nearly everything is free.
Definitely Dota 2. I think Dota 2 looks much better graphically, HoN champions look pretty bad in my opinion compared to Dota 2. Maybe you think HoN looks better from an artistic style?
Anyways, I believe that HoN will die eventually since the community is quite aweful and with the game supporting this "in your face" attitude then it's pretty clear that new players won't stay for long.
I've never played HoN only looked at videos, didn't like it. At the time there was no dota 2 and it felt too much like dota 1 ripoff. When I got bored of dota 1 some friends went to play League, I joined for about a year. It was better graphics after dota1 but the mechanics and community of immature kids made the game stale quite fast.
now that dota 2 is "out" I'd have to say I do enjoy it quite a lot more than League. The community still has problems but it's a lot better than dota 1. For example, there's been like 3 leavers and there's been like 1 game when support didn't buy courier out of over 200 I've played. You still get bad games where the skill gap between you and your allies is tremendous, but it does seem like there's a lot of people who are playing dota for the first time and still trying to learn, so I cut them some slack instead of flipping out on them.