I've had both.

Been shopping at REI since it was a little co-op in a warehouse on Capitol Hill in Seattle. Now it's a big multi-tentacled corporate monster...

REI's quality is about the same as LL Bean. I've got no complaints about either.

REI has a search function on their website that lets you select things made in USA, which is nice if you're the sort of person who wants manufacturing jobs to exist in the US.