Both have GTX. Both are insulated, but the EXP has more. Approximately the same warmth as say the La Sportiva Nepal Extreme. The EXP is a little higher in the cuff and is considerably stiffer in the midsole because of the carbon fiber shank. The GTX has a nylon midsole that is pretty stiff but flexes more than the midsole in the EXP. In my opinion, the EXP is a better ice/mountaineering boot, and the GTX is a better general mountaineering boot. The EXP accepts step-in crampons a bit better also. The best thing about the EXP, I think, is that it is orange (swtiching to red this Spring) and the GTX is blue. Brighter colors always make you look cooler in photos. Hope this helps.