First off: The baseline: I have a stack of SLK's size L and I love them as they just fit nice and the material is great - smooth and soft. I've now had them quite some time and they maintain their shape nicely even though I abuse them by washing them with my other washing at 40 and not as per their washing instructions. I particularly like the SLK because of the narrow elastic band. It simply doesn't roll!
So now The MAX XX (L): By comparisson I would say the material is even slightly better - really smooth and nice to wear (maybe just because they are new compared to my worn SLK?) The fit is with a bit more lift than the SLK so I actually like that even though the SLK lift is totally comfy. Where they don't quite shine as much for me is the waist band. Initially it didn't roll but after some wear and washes after it lost it's original stiffness (no pun intended) it did start rolling just like any other wider elastic band that most underwear have despite myriads of claims they don't and never will. Now, I'm not especially huge but also not skinny so I'm aware that your physic will play a role if that happens or not. Would I buy them again: I will definitly buy another pair to wear for some months to discover if they become a permanent fixture or not but I will most definitly stick to my SLK undies - simply because I hate any rolling elastic!