Dolly is incredible with Bernadette. BUT, Once On This Island is incredible too, and that production will never be able to be replicated outside of Circle in the Square, so I'd go with that one. And the performances by that ensemble really are outstanding. Dolly will tour, albeit with a different cast, pretty much in the same form and with the same direction/choreography/staging it has now, so you could catch that later and get a really similar experience.