The 2006 release is very much a product of its time, and the sound quality was pretty mediocre even for that time--largely becuase a lot of the transfers were made in suboptimal conditions and also because restoration of acoustical recordings is a craft that few fully understand. Doug Benson did a pretty good job, but I don't think there were many people back then who really did the intensive study needed to maximize the acoustical sound. There are all kinds of peaks and valleys that are much easier to address nowadays with spectral restoration software.
Rich Martin, the restoration engineer for Archeophone, on the other hand, has been working exclusively (I think) with acousticals for decades and is on the cutting edge. This entire set is head-and-shoulders above any prior release--extremely listenable, even to modern ears. Hardly any resonances to be found, and he maximizes the signal-to-noise ratio with virtually the minimum possible spurious shellac noises. It's hard to overstate how much work it is to restore an acoustical recording. Even the clean ones are filled with clicks and noises that click removers can't transparently address and require dozens of hours of manual cleanup. Even as someone who loves doing it, it's excrutiating work.
As someone who has spent a lot of time studying acoustical recordings myself as something between a hobby and a serious pursuit (I'd do a lot more of it if I didn't have a day job and a toddler), I only have a few minor differences with Rich's mastering, and some of this may be subjective, and I mean these criticisms in the most constructive way possible: I think on a few sides, there's more bass to be brought out, especially those with bass saxophone. It's a delicate balance, because the bass is buried in shellac noise and it's hard not to bring a bit of rumbly noise along with it. Having a few raw transfers of clean King Oliver records, I also prefer a bit more bass and rhythm and a bit less shreiky lead horn. Bringing out the high frequencies too much can bring out some of the horn resonances. Still, though, I'd grade the 2006 release as ~6/10 and this as no worse than 8.5/10.
The entire package you get here makes this a must-have. Ricky's notes are essential, and the supplemental CDs are illuminating.