The MaxxAir fan is standard on the Advanced RV Class B. I don't think it has anything to do with stealthiness. It is just much better than a Fantastic Fan and I would have to assume it might cost more. In a competitive situation Fantastic Fan is most likely what you are going to get.
With MaxxAir the cover is is integral with the fan. When we had the Fantastic Fan the rain sensor often got confused in high humidity dew situations and if you camp a lot on the coast expect the the mechanism plunger device to corrode and fail.
Our MaxxAir is a 10 speed remote control model and the first thing I noticed was it was a lot quieter than the Fantastic Fan.
The roof hole is the same 14" square I believe so I would think the fans could be interchanged.