I wonder what the deal is there. I need to get another optic and mount it on to my X5 Legion to compare apples:apples, but I'm pretty happy with how load development is going for my X5 original (is that what we're calling the old ones?). I still need to try loading up some of the 115gr HAP and Zero 125gr JHPs I have, but so far it's pretty accurate with 147gr Zero JHPs. These groups are from a crappy 2x4 rest at 25m. Note I was adjusting zero between groups, it's not zero shift inherent to the load.
I will say subjectively the slide to frame fit is tighter on the X5 OG than the X5 Legion, and the slide to barrel fit on the X5 OG is bank vault, zero play in any direction. I'm legitimately impressed with that aspect. The slide to barrel fit on the X5 Legion is fine, about on par with other good quality pistols.