I'm currently training an old former USAF C-141 pilot who recently bought a Lancair ES with a GNS480 and is trying to recapture his IFR skills after quite a few years of only VFR flying. It's taking him significantly longer to learn that unit than folks usually take to learn a 430/530. That's not an inherently bad thing, just a result of the power and flexibility of the 480, which is more reminiscent of a modern transport category FMS than a typical light GA GPS/nav/comm unit. As such, it has a lot more capability than the average personal aircraft owner/pilot needs, so the additional effort to learn its complexities has little return when compared to the GTN650/750, which are a lot easier to learn.
One barrier to training with the 480 is the lack of comprehensive high quality training materials such as are widely available for the far more numerous 430/530 systems. That shifts a lot more of the learning process to one-on-one training with a CFI who knows the unit. I can have someone with a 430/530 spend $110 and go through this training package, and they're pretty much ready to jump in the plane and start applying their knowledge under instructor supervision. OTOH, with the 480, I have to spend a lot of hours working with the downloadable simulator before they're ready for that.
So, if I were buying a new unit of that sort today, I'd choose a GTN750. If I were buying a used unit, I'd choose a GNS530W. But if a plane I wanted already had a CNX80/GNS480 installed, that wouldn't be a barrier to purchase, and I would not give it any greater or lesser value compared to a GNS530W or GTN750 installed in the same plane.