I haven't tried that scope in particular....but my experience in general with the XTR II lineup is that the lower magnification scopes in that lineup are better than high-mag scopes.
My other general rule is that I'll almost always take clarity over magnification.
I've used 5-25 XTR II scopes that were nearly unusable at 25x - you had to go down to 16x-18x before the clarity was decent, although they were certainly usable by 20x. So if you're thinking these are going to be decent at 40x, my guess is that they probably won't be great. But I have no experience with this particular model, so that could be wrong.