We have gotten two sets of the Sunsure cushions, 1 for a Hunter 25 and 1 for our Hunter 28, I can't speak to the Bottomsiders but besides the quick response on the order once placed, we've been extremely happy with both sets. The fit was perfect, the white Sunsure fabric has been easy to maintain and clean and my tender tushy likes the firm feel of the cushions. Our dock neighbors are all jealous of the cushions and always ask where we got them.
We use the boat mostly on weekends so take the cushions in each Sunday and bring them out for the weekend. I usually keep them out while sailing and even without the supplied snaps (I choose not to install them) the cushions generally stay put on the nonskid seats.
For our next boat we'll definitely order another set.
Good luck
Victor