I'd go with Groundhog Day simply because of Andy Karl. I think Sweat is a much better play than Groundhog Day is a musical, but I don't think there's anything special about this production of Sweat. I'm sure Sweat will be popping up in regional theatres for years to come, while this is probably your only chance to see Andy Karl in Groundhog Day, however, and he's excellent.
Depends on how you prioritize these things, however.