I've had Willie&Max compact slants (look good but waaay too small).
3 sets of Saddlemen Jumbo Slant Drifters. The warranty is excellent (3 sets so I speak from experience). The backs are plastic, plain and simple, and mine cracked in 8-10 months enough to make them unuseable.
Am now using
Tourmaster Cruiser IIs. They are way more substantial than the Saddlemen. I got the regular box, not the slants, since it just seems that the regular box makes more room.
I use the bags to carry stuff. Rain gear, extra gas, tools and that sort of thing. The bags that cracked weren't worked more than I would have expected, but maybe I expect too much. There are a couple of other guys who've had Saddlemen fail in a big way.
But they do look good!