There's a discussion of the Cap4 over at backpacking light, with mentions of the Spyder and T2. One user says Cap 4 is lighter than the Spyder; another didn't like the feel of the T2 against the skin. The whole thing is here:
By Dom Administrator From New Brunswick Canada Nov 2, 2012
Are you sure the MEC T-2 doesn't have thumb loops? I have a 2 year old Mec T2 and it has thumb loops. I never used them though. I find it's a gimmick. YMMV. If I were you I'd get the Merino option that Johnthethird gave as other options.