First, make sure your straps are in the right slots. They should be in the second slot, the ones furthest away from the toe.
The SL straps are leather and conform to the boot easier. The Atlas straps are made with something else. Its a little more rigid and doesn't let the strap conform as easy to the boot. I found it gets more broken in and takes the shape of your boot the more you use them. But yeah, the SL straps are the shit.
dude thank you so much I was going crazy. Yeah I do have them in the right slots but thanks for checking. I had Union send me another set for the Atlas thinking that would solve it. I even took both the SL and Atlas straps off to compare size. Maybe the answer is to get a set of SL straps to get them fitting faster.