What do the dogs prefer? Personally, I'd do both :-) Beds for the dogs when they are on their own and a couch that you can share when you are present as well.

What size are the dogs? How old? Might there be physical limitations getting on/off a couch?

Our dogs are usually not allowed on furniture ... we buy really nice dog beds from Orvis ... but my son was letting our old small dog hang out on a chair in his room when he was home for the summer. We ended up at the Vet ER for 4+ hours because she did something to her back when she jumped off on her own. She recovered, but not worth the pain she had and our worrying, so the no furniture rules are being enforced!

I personally prefer couch because you can share with your dogs

You mean a couch for dogs? They do make those.