Armorgames focuses more on fighting games IMO, while Miniclip has more genres in gaming. Also Miniclip has other sites' games such as Runescape. So I think they're pretty even.
I personally prefer Armor games because of all of the different things that you can do besides gaming. I also like how Armor games is not a "leech site" like Addicting Games can be. (Miniclip is not one either)
Definitely AG. Miniclip has (as people have said) minigames and the community is horrible. Some of their games are good in a minigame standard but AG's games (most of them) have plots to them, and sequels to the games, keeps the player wanting to play more.
You can't even compare these two sites... Miniclip has no Forum. And were all being biased.
I like the Miniclip achievements system better than the one on AG, yet I lik e how there is a forum on AG. The reason I like the Miniclip achievement system better is simple, you can compete globally with members for a better score. I've gotten multiple scores in the top 99% of the world, and I like that. But forums trump all, plus Miniclip is 'G' rated.
AG by a slim margin.
If your wondering why it's a slim margin it's because some of the games on Miniclip are more fun as a multiplayer and as a whole.