I would say MCR because when I saw them live, I absolutely loved it over the performance I saw by AFI. The albums for both may not be so great but their live performances are what I mainly look for.

MCR sucked when I saw them, AFI was amazing.

^ I will agree with you that a couple of times they have not been good performance wise but other times, I have seen some amazing shows.

I'd say MCR because I havent listened to AFI much and couldn't nreally comment. Plus I did actually really like MCR at one point, then they just got boring.

AFI definently, I've started to love some of the songs on DecemberUnderground. It's definently not their best album but there are a few enjoyable songs.