Hi Debora, Conventional wisdom holds that 5.1.2 is preferable to 7.1 as rear speakers do not convey much sound where as the 2 height channels would allow you to enjoy Dolby Atmos “object based sound” which can be very immersive. This assumes you have a receiver with this capability.
I actually have rear speakers and ceiling speakers and like having both. In all honesty, there is no right answer, only personal preference. It would be great if you could hear some different systems or experiment in your own room.