I had a UL and sold it after a year. I don't know if I just didn't have the right cab for it at the time, but I just remember it feeling anemic and ice-picky, even at rehearsal/stage volume. I really think it was the cab, though, because everyone else seems to have much better experience with it.
I've had a Sig:X for almost 10 years and have never regretted it. I also have a CLX. Both are incredible amps... but the Sig:X green ("Clean") channel is one of the best clean sounds out there... channel switcher or not. That channel alone is worthy of exploration, especially if you can crank it.
The UL's clean channel, IIRC, was super high headroom clean.
I also have owned a D60 and D120. Both were incredible amps. The D60 actually did the VH and cranked/modded Marshall thing really well IMO but with bigger balls. The D120 sounded massive. I ended up trading up from the D120 to a Sig:X and haven't looked back. At the time I was really in the market for a Bogner Ecstasy 101B. When I plugged into the Sig:X, it actually reminded me of the 101B... if you took a blanket off of the cab. It felt like the Sig:X did everything the 101B did, but better. YMMV obviously, but that was my takeaway.
I think the Sig:X is underrated among the Fryette offerings.