I have both. Much prefer the Thor, but I also only hunt during archery seasons and the Colorados run a bit warmer. I have multiple pairs of Thors, I probably wouldnt buy the Colorados again. Not because they arent a good boot, but the Thors just work for me. The Colorado feels bulkier on foot and has a flatter toebox while the Thor is pointier. Kind of hard to explain that one, Ill try to show it in the pics. I wear 9.5 in both, but the Colorados feel like they have a touch less length (probably due to the profile of the toebox). I typically dont like a lot of ankle support, the thor doesnt have the ABSS and the Colorado does. The Colorado has a lace lock after the first 4 eyelets and makes it a bit easier to tie them. The thors (I think some of the first iterations had a lack lock) have no lack locks and you have to find your method to tie them - which Ive noticed prevents me from overtightening.
The Crispi website lists both as a flex 4, but the Thor is noticeably stiffer to me. Id put the Colorado closer to a 3.
I have Thors, Makra Trek and Combi, Zamberlan Sierra 700s and the Colorados. I prefer all of those boots over the Colorado. Not because I have complaints about them, I just prefer a stiff boot that doesnt feel like a lot of boot and has a more athletic feel in the upper.