What makes the 120th Anniversary special? Is it special at all? Let’s take a look and compare with a standard 6118T.
Before I begin the comparison, there are a couple of things about the green Annie that I should mention:  The guitar was always appealing but lacked a certain amount of sustain and robustness UNTIL….I replaced the stock Space Bar bridge with a stainless steel Tru-arc. That really brought the guitar to life with that little bit of extra sustain that I was missing and provided a much better frequency response. The other change that I made was the replacement of the HS Filtertrons with TV Jones HTs. I love these pickups! Having said this, I will make comparisons based on physical differences and response, with a nod to the actual sound as the pickups are very different.
The first thing I noticed is that the 120th Annie is heavier. I believe this is due to the extra metal in the Bigsby and the fact that the 120th has a slightly thicker top. The response of the 120th is closer to that of a solid body. Not that it responds like one, but it’s a bit more in that direction than the thinner topped green Annie.
As a result, the 120th is better suited for use with overdriven sounds and processing. This difference in weight with the thicker top and the different pickups (the 120th comes with TV Jones Classics) are the most defining differences between the two. It is interesting to note that the 120th was built in June of 2003, right around the time when tops were becoming thinner. Perhaps the next one to come off the line had a thinner top; who knows.
The 120th was built at the Terrada factory and the green Annie was built in 2005 at the FujiGen factory. A few other differences are  the neck extension on the 120th is flush with the top while the green Annie is suspended. (see photos)  the headstock on the 120th is 16th of an inch wider  the 120th has an ebony fingerboard while the green Annie has dyed rosewood (this probably adds a bit to the weight of the 120th as well)  the pickups, as mentioned, and the stock roller bar bridge on the 120th.
The one other thing that separates the two is the fact that the green Annie has a shallower neck angle than the 120th. Was FujiGen using a different template than Tarrada? I wonder how this compares to a vintage one. Some will say the lacquer top on the 120th affects the sound. My sense is that the other physical characteristics completely override any perceived difference. Namely, the lighter build, suspended neck extension and the shallower neck angle of the green Annie. Also, none of the modern Gretsch pro-line guitars are smothered in plastic finish like some other guitars.
In summary I would say that they are both great instruments; both are the most comfortable guitars I have ever owned. I have bonded with the green 6118 and it is a somewhat unique instrument due to the physical attributes mentioned above. If anyone wants to hear it, go to my web site and stream the latest CD although keep in mind that it is low quality mp3 format on the site.