In my opinion, you can still likely be able to get very similar results if you use the App and Ratbuddyssey it would likely take more effort and longer obviously. The difference between the two version is just the resolution, so the one with much lower resolution will naturally be less accurate, and even with the App, it will take more trial and error, to get the same results.
Also, imo, let's say XT32+App+Rat get help you achieve +/-2 dB 20-120 Hz, and XT+App+Rat only +/-3.5 dB, I highly doubt anyone can hear a difference, but they can definitely see the difference by plotting the FR with REW. So it boils down to a theoretical better vs a practically no difference.