In answer to your question, I think it would have to be determined on a case by case basis depending on what their H/J experience entails.
On the plus side it can mean they have already been in groups and at various show facilities. They may have been handled more. They may be good at loading. If they have had what I think of as good hunter/jumper training, it can mean they have been allowed to find a natural balance and learn to move in rhythm with freedom.
As I’m sure you know, training in any discipline can vary greatly both philosophically and by the skill level of the practitioner. H/J stuff can work against you in either of two ways. If the “experienced” horse has been taught to expect passivity, you could be looking at a terminally on-the-forehand animal who is insulted by any meaningful contact and wants to do auto changes whether you ask for them or not.
Alternatively, another unpleasant possibility is “He failed as a jumper. Let’s dump him on some unsuspecting dressage person.” Watch out for code words that mean “draw reins” or “fried.” In short, while I certainly wouldn’t rule out a horse with a hunter/jumper background, I would look very carefully at what each one brings to the table.
As for a greener, less experienced horse, the question is always what surprise is lurking beneath the surface waiting to nail you when you get him home. I would advise against dead-green, but otherwise, I certainly think you can cope with a green horse and make him into something. The obvious priorities are temperament, movement, and uphill balance.