According to several articles based on SIG’s press releases both have the same sized window:
https://www.guns.com/news/2023/07/18...24mm%20window.This allows for a sight picture with less distortion or "fisheye" while having zero magnification. The Romeo X Pro, left, and Compact, both have a 1x24mm window.
Which is the same size as the window of the SIG M17 optic. Makes sense given the Romeo X optics are simply open emitter versions of the M-17 optic.
Having had the opportunity to play around with the M17 optic on an M18 pistol, I think Noah is onto something with his argument. That window size doesn’t tell the whole story and how low the window sets to the fulcrum has some effect in actual use.