As someone who has put time into both games, and never played DotA, I prefer LoL. My name in game is plantains.
As far as the HON vs. LoL debate, I love how HON looks graphically, but HON can also turn into a clusterfuck of effects very easily and its very confusing as to whats what, granted I played HON on max settings, so maybe its easier to distinguish shit on lower settings. LoL's effects are very easy to distinguish, whether its sounds or ingame graphics, so I always know what all the other champs are doing, even in 5v5 teamfights.
Shop wise, I have to believe that anyone arguing that the HON shop is better has never played LoL. Its no contest. LoL has the simplest categories ever and the tech tree for items is easily accessed. If you don't know, heres some catagories for the shop in LoL: Attack (stuff that increases attack), Lifesteal (stuff that gives lifesteal), Attack Speed (stuff that gives attack speed). Every item page has a section that shows all the things that the item builds into, and you can click those to pull up the WHOLE build, where you can buy parts individually or all at once. Also, when the shop is open, you can click on any item you currently own and instantly go to its item page and see what it builds into, letting you build all or part of complicated items in only a few clicks and not having to go through tons of different pages to buy all the items needed.
A lot of the HON fanboys here are also complaining about how you can buy heroes in LoL. I find this hypocritical since HON costs money to play at all, and in LoL, you never have to pay money and you are at NO DISADVANTAGE. All heroes in LoL can be unlocked easily by buying them with the in game currency you get for playing games. There are not "premium heroes" in LoL that you are at a disadvantage if you don't have, and the free champions that cycle ever week cover a broad spectrum of types of heroes.
Also, people are saying that low levels are at a disadvantage because they do not have runes. Well, first of all, the runes are not that big of a deal, the bonuses they offer are marginal and a level one ashe who knows how to play her will always beat the level 30 ashe, with a full rune page, who doesn't. Also, LoL uses a matchmaking system, level 1 players are never matched against level 30 players, unless they are in a party with level 30s. And even then, they bring the team ELO down.
None.