To put another nail in the coffin, none.
Bought a £70 XPS from ProAirsoftSupplies a year back, returned it within hours.
Bought a similarly priced (like £100?) G&P EOTech with EOLAD unit (granted this was a 551, not XPS), same issues as below.
Got that fancy XPS with all the updated markings and whatnot from DavesCustomAirsoft (like £160 for that and the magnifier, luckily I got it second hand) but was exactly the same.
Stupidly dark, heavily reflecting rear lense (great if I needed to get a glimpse of myself mid game). It was also somewhat distorted (slightly oval, rather than circle) with ghosting on pretty much every setting. Even the lowest brightness had it, just very faintly.
Moral of the story: Airsoft EOTechs are quite possibly the worst optics you can get. Which sucks because they are my favourite aesthetically.