IMO, the Clipper captain is correct; the Clippers are more true "sailboats" and Windstar has "sailing yachts" with significant stabilizers that keep the ship level at most normal sea conditions.
I've only done two Windstar cruises; the first one was Costa Rica and IIRC, we spent something like 85-90% it under sail. We had one day of rough seas, and that was just a lot of rocking and rolling, not heeling. When it wasn't rough, I don't recall much of a heel at all.
IMO, the Star Clippers are adventure sailing, Wind Star is charming, gentle, luxury sailing.