As a CT ex-pat who's been back in the area for past couple months, gotta agree with Black Duck over everything else listed here. When I worked in Fairfield used to love Archie Moore's burgers, but don't know if they're still around. Also, the burgers at Dinosaur BBQ are very good. I don't get the Plan B love. Been to the one in Milford, meh. I'd be very interested in The Chelsea though.
On the Moes v. Chipotle v. Qdoba... I'm not finding a reason to choose any of them unless it's purely a convenience/time issue. Nothing at any of 'em worth commending.