Sonically the cabs are voiced from aggressive mids (Baer on the left) to smooth (TC112-4 on the right). The 1203 sits in the middle, literally and sonically. You can hear the genetic connection between the 1203 and TC112, and the roll-off and smoothing switches on the 1203 can get it closer to the TC112 feel. As I tend to favor a fairly mid-forward and articulate tone (as evidenced by me playing the Baer for a couple years), I preferred the 1203 wide open, but the switches provided some nice color changes. I wasn't crazy about the sound with the port plugged though - was more open and spoke better (to me) with the port open.
I think the ML112 extended a bit lower than the 1203, but the Hathor had more meat in the low-mids. I am really sensitive to wooly low mids and have gotten rid of cabs that leaned that way. The 1203 gets it just right though. Nice heft to the notes but I never felt like there was any wool or lack or articulation. The 1203 isn't as aggressive as the ML112 in the mids and that can be a good or bad thing depending on what you're looking for. To me the slap tone with the 1203 was better than the ML112. Steuart preferred some of the chordal stuff with my Monarch 5 (E-C) on the Baer as it was really crisp/clear in the mids.
The TC112 is a much more "polite" cab. Steuart calls it "musical."

. It goes lower than the 1203, has a bit thicker low-mids than either the 1203 or the ML112, and is very even and smooth through the mids. The 1203 has a bit more bite up high, and the Baer has a lot more edge in the upper mids. One interesting moment was when I cranked the gain on the GK MB Fusion and got it to overdrive. The 1203 sounded spectacular with that tone. I switched to the TC112 and didn't dig it nearly as much.
So my take is that the cab is pretty much exactly as Duke designed and described it. I have 4 gigs over the next few days in 4 different venues (1 outdoor) and I'm going to just take a single 1203 and see how it fairs. My hunch is that it will carry all of them. Right now the 1203 is totally looking like a keeper. Perfect size and weight (REALLY portable). The tone is in-between the Baer and TC112, so Goldilocks would dig it. One other factor is that the 1203 takes EQ really well. I was able to dial in a tone that is pretty close to the Baer by adding some mids either at the bass or the amp. Much harder to EQ the mids out of the ML112 - that cab sounds the way it sounds, and is much more towards the Geddy Lee tone camp. Now my question for larger gigs is 1203 + ML112, 1203 x2, or 1203 + TC112-8.