^^ The nice part about XTZ is that it tells you the PEQ settings to use, then can measure your results against the simulation to verify results. I agree that would be more effective, particularly in rooms with bass resonances (and whose does not??), than dialing for flat. REW can do a similar analysis, but not as easily.
I had commented to Classe that it was a little messy to figure how to get a test signal into each channel alone, so they added the wideband pink noise generator that comes on automatically when you enter the channel's EQ menu. That can work well with a decent RTA (better than 1/3d octave) for the main speakers. If the RTA can sample and average the space around the MLP, that can lead to better results than a single-point measurement if the responses are not uniform.
No matter what method is used, lots of listening is needed to really decide if the tuning was successful or not. One thing that's nice is the SSP can store the entire user settings into a separate memory. Then you can mess around with the settings, and if you want to erase all that, just recall the stored settings. This is done from the service menu accessed by pressing Menu>F1>F2>F3>F4. Unfortunately, it does not have 2 memories so it cannot alternate. To do that, you have to save/load from a PC. Then you can save infinite setups, but it takes a few minutes each time.