Gameplay
In HoN, last hitting/denying means that you can shut down the carries in your lane by preventing them from farming up. The downside to this is that melee heroes or ones unable to harass/deal with harassment are at a severe disadvantage. LoL removed denying for this very reason. The pros and cons with removing denying in LoL is that on one hand, it means that tanks and non-carries don't have to worry about getting their farm. The downside is that carries are free to last hit and farm in a lane, becoming more powerful. In both games, you still have to last hit. Saying that "HoN takes more skill" is just retarded because you still have to have control over your champion in LoL in order to get gold from killing stuff.
As for heroes, HoN's heroes had some serious balance issues when the beta was over (I'm looking at you, Zephyr). While I don't know how the current state of things are now that the beta is over, but I imagine it hasn't changed much. There aren't really any champions in LoL that can kill multiple opponents alone unless they have been severely fed (which is true in DotA, LoL, and HoN). However, in HoN, it's not uncommon for a hard-carry to tear apart entire teams once they get a specific item. Currently, the two most overpowered champions in LoL are Soraka and Heimer, both of which are support champions, who require decent teammates to be broken. One thing I like about LoL is how team composition is the key to countering champions, whereas HoN specific heroes counter other heroes (Vindicator vs. Tempest, for example), making LoL even more team-oriented.
For spells and abilities, HoN takes the cake. LoL is currently all about harass and kiting, backing it up with healing. This makes it incredibly difficult to initiate, leading to 10 people staring at each other next to a turret. In HoN, the maps are bigger with more areas to gank. Combine this with some quick nukes, and it makes it much easier to start a teamfight when it's 4v5 or 3v5 to begin with. Not to mention, there's a longer distance in between each tower, making it easier to chase. HoN also has much better stuns and crowd control, whereas LoL lacks champions able to set-up ganks or teamfights, especially with the summoner spell, cleanse. While LoL may seem quicker and more fast-paced with spamable spells, the reality is that the game oftentimes feels stagnant with neither side able to deal any damage to the other because they are too nervous to move in.
I prefer HoN's items, especially the bottle, the portkey, and the powersupply. These three items would fix a lot of the problems currently in LoL that I mentioned above. Portkey allows for teamfights and ganks to happen anywhere, powersupply helps you kite or chase or push and negates the effects of spamming spells, and bottle allows you to do the effects of both to a lesser extent, especially if you have a powerful rune. A few of the regular items in LoL seem redundant or imbalanced, such as stark's vs. malady. That's a minor problem, however, since both games have a unique variety of items to chose from with none of them being entirely game-breaking.
Gameplay Summary:
HoN is centered more around carries and protecting your team's carry. LoL is more about the team as a whole. LoL can also be stagnant at times due to having very few nukes and stuns and more harassment and healing spells. HoN has some balance issues with its heroes, considering some of them simply able to just roflwtfpubstomp entire 5-man teams all by themselves.
