A trimaran offers better seakeeping:
Let’s consider both the trimaran and the catamaran heeling by 12°, which is the safety angle not to be exceeded on a catamaran. As shown in the graphics, the Righting moment (GZ) is much higher on the catamaran than on the trimaran. A high GZ means more brutal and uncomfortable seakeeping.
At this angle of heel the catamaran’s GZ is double that of the trimaran.
Therefore, sailing the trimaran is much smoother than sailing the catamaran.
The trimaran has less roll motion than the catamaran, as the center of buoyancy is never far downwind like on a catamaran. Again, centered weight is the key to success and comfort.
In fact, all significant heavy equipment is located in the main central hull on a trimaran whereas it is distributed half and half in each hull on a catamaran.
This superiority of the trimaran is even more significant in heavy seas as shown on the illustration here-below.