Dreamhorse is easy to search for buyers but they are more expensive than other sites to list and they don't like you to put links to videos.
Equine.com has horses that are a little cheaper than Dreamhorse and they allow multiple pix and video links for the same price as Dreamhorse.
EquineNow is free and I've actually gotten more hits off of it compared to dreamhorse and equine.com. They allow video links.
I also have my horse listed on Warmbloodsforsale.com. They are priced right and you get a lot of pix.
On EquineNow and Warmbloodsfor sale when you update your ad you move to the top of the search lists, unlike Equine.com and Dreamhorse. A huge plus. All you have to do is look at your ad under the edit screen and it's considered changed - you don't really need to change anything.