I've used both
Like Dick down below, I have BS on my boat and we adore them. And have had them for 8 seasons. They conform to your shape for comfort. The darker the color, though, the hotter they are. Ours are white and don't have any problem with heat - even on the hottest days. And are not difficult to clean - only more frequently. Some friend took our recommendation and bought royal blue. They love theirs, but they do get hot in the sun. I've had mesh on several charters that I have done in the BVI. They were royal blue (know who I chartered with?) and were comfortable except the mesh stuck to your skin in the heat. Plus, after sitting on them for any duration, you develop a case of "boat butt". That is to say they get itchy where you make contact with the seat. The mesh also takes a bit of time to dry off.My choice? - Bottom Siders.