i'll never live down calling the tc112 "musical" . . .
(but the 1203 is likewise in that ballpark.)
todd, as usual, quantifies things quite well.
the caveat on this longwinded bit that follows is that we did this over the course of about two hours, so you don't get the dialing it in thing you might do as you learn about a cab, and how you, your basses and your amps interact together over weeks/months. we generally favored the monique as the test amp. i prefer the puma for *my* sound, but the monique gives you a lot to work with
i've been playing through the tc112 (4ohm) for a while now, so i like that sound and am used to it. the 1203 def comes from that audio/design perspective—for me that's a good thing. the 1203 has more high-end sheen than the tc112. for me, i'd want to dial that back through eq or the switches on the back—or not. both cabs have very attractive sonic capabilities and usefulness (as does the baer)
as todd mentioned, it seems like you can get the 1203 closer to the baer sound through application of midrange from either the amp or onboard eq from an active bass. seemed harder to get the baer back towards the 1203. my guess is that each of these cabs could make you happy if you worked with it a little (cause i don't think anything is "perfect" for everything) . . . three shades of awesomeness.
the 1203 handles the low notes on a b string pretty well, imo. i know some guys have different needs in this regard, so it's ymmv. still it worked for me—i liked it better than the baer for the low notes as that cab's mid thing kind of obscures the lows for my taste. the tc112 wins for best b string in comparison to the 1203. but the 1203 *is* really impressive for the low notes.
also, i felt like you got a lot of string character/nuance out of the 1203. there was clarity without it being "ganky" (that's scientific talk). and that was with very dead strings on my basses and semi-dead strings on todd's basses.
i do some really percussive things on the strings and the 1203 was great for those.
for my ears, slap was better on the 1203—though it does have a little of that "studio" thing, if that turns you off. the baer's midrange thing was hard to deal with for me on this.
the baer's midrange thing means that the notes in close chords tend to mush together a little—which i like (i want to hear the beats and so forth). adding some mids to the eq when going into the 1203 helped this out and there also seemed to be more clarity overall. i like what the tc112 does on this a lot, so that's my benchmark.
harmonics were good across all three. the flavors were a little different, but they represented well (could get the 9ths on the c strings, etc.). the 1203 and tc112 won over the baer for how they decayed (hearing beats in the minor seconds, etc.)—at least for my taste. (this is one area where i'm not sure i like the monique, so it's hard for me to tell.)
the 1203 sounded more compressed and less open than the tc112.
of course, one of the hooks for the 1203 is the portability factor. in that regard, it's way better than the baer and better than the tc112. part of the reason some people were pestering duke about doing a cab like this is the metro-bility of the cab. it does this with flying colors and sounds really good in the process. i've taken the tc112 on trips through the l.a. metro (!) and while it's not impossible, smaller is almost always gonna be better in this situation.
one thing todd didn't mention is that this seems like it could be a very good cab for upright players. nice low end and the 3-inch speaker might be good to give presence to the string sound. might be worth a listen.
i have two tc112s. at some point i will have a 1203 (or two).