OK, here is my humble thoughts on this:
Personally, I will always go for single 112 cabs. At 58 (almost 59) with the lifelong effects of Polio, I like my gear to be as modular as possible. I have weighed all the options, and tried many of them. The single modular approach always works for me. If I need 1x12, 2x12, or 3x12 I've got the gear to drive them. I have the gear situation covered now and I like the way it is working for me.
On to the type of cab and tone:
I just ordered a TH500 AND two 1203 cabs. Why? Honestly I wanted a light solution for rehearsals and some possible use on gigs. The TH500 is one AWESOME head, and that is comparing it to a Monique/ProLITE rig and two Thunderfunk heads. I'm not saying it is better, they are just four different flavors of great! I used the TH500 at rehearsal last night with a GS112 and it rocked, however, I still sounded like me.
I could use the Aguilar head and GS cabs and be totally happy. But I like Monique and I am really looking forward to using the 1203 cabs from Duke! I am quite sure I will be satisfied with Dukes cabs, and will be able to get the tone from them I want while still sounding like me. They will just be different tools to get the job done.
To this point I haven't played any cab where I wished for more low end. I have wanted more mids without excessive EQ. I think I'm gonna get that with the 1203s. My goal is to simply have a cab with more mids so I will have more options with my EQ.
Now, as far as your situation:
I would think that the 1203 cabs would be more similar to the Baer ML112 from what I have read and from talking to different folks here on TB. Didn't you gig the ML cabs? If so, you can probably assume, at least tone wise, that there is some similarity between those two makes. It sounds like the TC cabs are much smoother and rounder. Will the weight/size of a TC212 cause any challenges for you? What about the option of two TC112 cabs? Would a option like keeping your TC115 and then purchasing a pair of cabs for big gigs work?
Nostatic is currently testing a 1203+TC112 combo with success. So currently he has 2x1203s and a TC112. That sounds like a good combination especially if he can use a 1203 and the TC112 without any ill effects. You have so many options to choose from. We all do. I mean really, look at the gear listed in your post and my post. That is pretty exciting!
Personally and IMO/IME, no matter what gear I use, I generally sound like me. But I am blessed to be able to afford awesome equipment, and I have fun playing out, so why not? At the level of gear we are gigging and have to choose from it really hard to get a combination that sucks. It's just different flavors of awesome. I think that is where I am now, just mixing it up and trying out awesome gear.
I hope my ramblings help somewhat, or at least give you something to think about. Ain't it fun to gab about bass gear?