Depends on how old you are talking about. Collins has been around a long long time. They have been under different ownership though throughout their history, and this can lead to variances in the quality of their axes.
I have an older Collins axe, a Legitimus single bit which I find to be of excellent quality. I then have some that were still under the Collins label, but basically made by Mann Edge Tool Co out of Pa. Basic rule of thumb that I have found with Collins, the older, the better.
Attachted is a pic of another one I just picked up - check out the lettering on the label. Though the quality of the tool, to me, is superb. (not the legitimus one I am talking about above, this is another one)
Not sure if this helped or not. As far as in comparion to a GB, I don't have enough experience with them, though I would take my Legitimus SB axe and compare it to mostly anything.
Edit - inlcuded the SB Legitimus pic too now.