It’s generally easier on a mountain bike, Charge Spoons and SDG Bel Airs have a pronounced “hammock” which helps you sit in a consistent position. So if it fits your arse, you’re laughing.
I find WTBs are more of a solid perch and the shape/width just seems to cleave me in two!
I can pretty much look at a roadbike saddle and tell whether or not I’ll get on with it. I like narrow, flat (front to back) and rounded (side-to-side).
When I had a long, low and racy hardtail, I preferred saddles similar to my roadbikes – presumably because the position is more rotated.