I have speakers set up for 11.2 however my receiver only supports 9.2 at one time so I must choose between height and wide. I’ve tried M22, M2 and QS8s as both height and wide speakers and found that in my room the M2s were indistinguishable from the M22s in both the height and wide positions. The QS8s were superior to the M2 and M22s in the height position though I’m not sure the additional cost is worth the improved dispersion for most people (I had the money so I went for it). OTOH the QS8s were inferior to both the M22s and M2s in the wide position. So in summary the QS8 was the best in the height position while the M2 was the best in the wide position (matched w/M80 mains). However, I’m not sure I would recommend paying extra for the QS8s as height speakers rather than the M2s unless money was no object.
No, the height speaker doesn’t even come close to adding as much as the side surround channels. How much it adds in comparison to surround back or wide channels is IMO very room/seating dependent. When I have my main speakers spread out to 45 degrees or a little more I find that the height channel adds more than the wide, however, if my mains are kept up front under my screen then the wide speakers add much more than the height channels.
In comparison to the surround back speakers again it depends on placement. If you can place your side surrounds such that they create a solid phantom rear soundstage then the height speakers add more than the rears. However, if placement issues preclude this then surround back speakers will add more than height speakers.
One place where height speakers do help out is when you have a very large screen. The height speakers can make the front soundstage sound fuller like a wall of sound rather than localized below the screen if that’s were your speakers are.
Note that the only sounds coming from the height channels are ambient one. They only come into play with music, rain, wind, echoes and other ambient sounds so often there is actually nothing much coming out of them. OTOH wide speakers are almost always playing something and if placement issues require a narrow placement of your mains then wide speakers add quite a bit by expanding the front soundstage so it wraps further around your seating.
