It's a mixed thing in our house - one cat scratches ONLY on her scratching posts (good kitty ) the other will only scratch the carpet and my big leather chair (the arms are like couch arms)...she never touches the fabric couch - just the leather chair - frustrating as can be - and the chair looks horrible!
I think, as in everything else cat related, it all depends on your cats surface preferences for things...when I was growing up we had NO trouble with cats and leather furniture - but with our kitty now I know our next couch (we are currently shopping for one) can't be leather...
Could you get a large swatch of leather just to see if your cats are interested in it? I know it's not the same as the full upright couch, but you might get a sense for whether they like how it feels on their paws.
We did something similar for testing out microfiber -- we bought an ottomon to see if the kitties were interested in scratching it. When they left that alone, we felt safe buying the couch.