Tough call. I think most of the recommendations I've read is to go with wides first. I haveread a smattering here and there from some people who prefer height over wides though so YMMV. I would just try both and see which you prefer.
What speakers were you going to be using for the wides? I tried the wide setup, I preferred it, but my spouse did not. My living room looked like a speaker lab, but I thought it sounded more expansive.
Ive ran both wides and heights in the past although not at the same time with surround backs...never had the room for them. I like both configurations, but I like wides more. Interestingly enough I did not care for heights using dsx but they sounded great using dolby PLIIz. Wides sounded great using dsx. Never had an avr capable of neo x so can't comment on how that dsp sounds.
Audyssey recommends wides before heights when using dsx.
I don't need snobs to tell me how to think, thank you!
I have also ran FH and FW at different times with my system. I like both, then what is the difference? I used the FH when things were setup on the long wall and now use FW with the setup on the wide wall. It also depends on the ceiling height of the room as well as how wide the room is for the system. Remember that these are not major speakers and provide spatial cues for the listener. For example my FH were 9 1/2 ft off the ground and with the FW speakers, they are 6 ft from the mains.