YachtWorld is my basis, so working from that...
1) one of my biggest complaints with YW. Is that there are so few criteria that you can search by. Generally only leingth, age, price
, and manufacturer. I would love to be able to seach by any other data points. Like SA/D, PHRF rating, fuel
2) if a seller has a recent survey
it would be nice for there to be a way to post it
3) no boats without pictures. These days there is no excuse.
4) links to reviews
of a particular design included with listings where available
All of these are of course available with a quick google
search, but having it all contained in one place would be nice.