I don't know what X-System is. I have read that synthetic fabric wicking material is smellier after use than merino wool. That is, when you sweat in the synthetic fabric, it evidently smells worse as a result of this sweating than does the merino wool. I don't know why or even if that is true -- just repeating what I have read.

I have Minus 33 Merino Wool long underwear and long sleeved top. I wear this under wool pants and a wool shirt when elk hunting. It feels and works great. I replaced my polypropolene underlayer that I have used for 25+ years with the Merino Wool just last year. The Merino Wool is a big improvement in comfort in terms of the texture and feel of the fabric on my skin. I guess they both worked equally well at the main reason I had them -- to wick sweat away and provide some warmth.