From my experience with the low numbers and the XL vault. The sunnies seem a bit different. The XM finish seems smoother and more refined, I think. Hard to describe, maybe its just knowing that they are such low numbers, maybe more care was taken in the final grinding or what ever they do. But I compare my low number to a 4 digit in the 6000 that I have and it is definitely a nicer finish, seems almost lighter in weight also.
Just my take.
Just my take.