We've stayed at SSR, BWV, BCV, VWL and our home resort, OKW.
I can verify what the others said about the OKW bathtubs being the biggest. I think the reason they may look smaller to you on the pictures if that the room they are in at OKW is larger than the other bathrooms. You have to be closer to the tub at the other resorts to take the picture, which makes the tub look bigger.