Ultimately, that's going to boil down to a head-to-head comparison of one specific make & model to another, of course. In very general terms, I'd guess that most, if not all, will be quite similar in pure output - if what you mean by that is simple volume/SPL - but not necessarily in terms of full-range tone at comparable output.
Perhaps the main thing that separates Acme, AudioKinesis, Baer, Barefaced & fEarful from the rest - apart from the direct-to-customer business model - is the presence of the relatively new Eminence Kappalite 3012LF high-excursion Neo woofer - or an OEM variant thereof - that makes available to each of those cabs exceptionally deep low end in a very compact package - something that, until recently, was very, very hard to provide. That, along with the superior engineering, well-engineered crossovers, and overall extra attention to detail, makes them something special.
The very best of the traditional boutique cabs (Bergantino, Epifani, Euphonic Audio, Mesa & others, as I've mentioned) are certainly competitive, however, based largely on the high quality of their own proprietary drivers & components, and expert workmanship. Main difference in tone, again very broadly speaking, will probably boil down to the more conventional voicing (relatively less deep low end) as determined by the more conventional woofer + tweeter orientation.
Do some searches on "Baer", "fEarful", "Acme", "Barefaced" and "ThunderChild" to start. Get a sense of what some of the other players think...
MM
P.S. Please take the above comments with a few grains of salt. In this case, I'm prepared to defer to lomo's experience. He's played a lot more of these cabs than I have.
