Not to compare apples and oranges, (I think origins should be compared with other origins, teamups with teamups, etc) but although I think Avengers was more well-rounded, better paced, and MUCH better written, I find MOS to be more satisfying, and have stronger moments that stick with me (Supes flying into the world machine and the Clark blanket flashback come to mind.)
I find MOS to have a lot of selective memory involved with some of its critics. "It's bleak and emotionless" (Well, then let's forget about the scenes of Clark with his mom, Lois, the priest, baby Clark being sent off, etc)
Again, I think Avengers was really good. And I think it deserves a bit of its acclaim. Where I think the fanbase goes wrong is to be like "Avengers was awesome, therefore this sucks."