The sport band is all I've ever used. Its so comfortable.
Yeah, I'd probably consider myself a rubber strap expert, lol, because I've spent so much money on rubber straps over the years for my mechanical watches, from $50 Hirsch to $250 RubberB, and I'm amazed at how the Apple strap is more comfortable than any of them.
That being said, I feel the same way about the link bracelet, when it comes to steel bracelets. I'd put the link bracelet up there with the best of Swiss watch bracelets, at least this side of the likes of Patek. It goes a long way in making the Apple Watch feel like a "real" watch, for lack of a better term.