Hero kills in LoL are great to pick up if possible, but since you lose no gold the only real downside to dying is that you're letting your enemy get ahead of you in farm. LoL heroes snowball pretty hard, so getting behind in farm is very bad.
LoL is fun and has a healthy FHC community, I'd play it and enjoy it. Try Dota2 for a few games (~10 maybe) when you get the opportunity (I don't have any spare keys, or I'd hook you up) and see what you think. The general opinion of FHC seems to be that they like both, although a lot of the really veteran LoL players here seem to be switching to playing more dota2.
In either case, play with friends whenever possible, it REALLY improves the experience. Pubs are okay but a team of friends with voice comms makes games awesome.