Saw both. "The Expendables" is a better film. I hate to say it, but it's true.
That said, I'm not a fan, in any way shape or form, of O'Malley's comic, finsing almost all of it too insanely "hipster" and hep for its own good, and hating all the chracters with a passion, that said, "Scott Pilgrim vs. The World" is a good movie. It has all of the comedic appeal that Wright is familiar with along with a wonderful cast and great sense of ignoring most of the things I hate about the comic (namely everything) in an attempt to tell a proper love-story with a clever use of metaphorical boss-fights and ridiculous situations to make it a stand-out comedy and excellent film.
"The Expendables" is, damned near, the perfect action movie, finally giving film-geeks like me something that we can really get behind in the form of a mash-up of some of the greatest action-stars of all time making a movie that is driven solely to showcase them in all their splendor as we see these men do what they do best in the format that best suits them all, made by one of the most talented action-directors of all time. It's a beutiful swan-song that, much like "SPVTW" will not be TRULY understood by anyone outside of its core-demographic (the people that didn't need to look up ANY of the actors featured, more or less), but both are great movies, in the purist sense.
Edgar Wright needs to get back to finishing the fucking "Blood and Ice Cream" trilogy, though.