Re: GSP 1101 vs 2112/2120
2101/2112/2120's sound way better than the 1101 imo. i own (or have owned) everyone of these except for the 2120 (and my friend owns that one) and i can honestly say that the modeling on the 1101, while great for what it is and better than line6 imo, is still not nearly as warm or responsive as the tone you get from those old tube preamps. additionally, the tweakability is much more simplified on the 1101, which depending on how patient you are, is either a pro or con. i dug the 1101 when i first got it, played the hell out of it and created a ton of user banks. but when i went back to my 2101 (the best of the 3 tube pre's imo) it just killed it tonally.
however, the 1101's big selling point is that it allows you to incorporate it into your current amp set-up, whether it be a tube head, pre-amp and power amp, or use the 1101 as the preamp into a tube power amp (you can also run it direct into a mixer or p.a.). it does not mess with your tone and allows you to just use it's effects. in this set up, it works quite well and offers something the 2101/2112/2120 can't. so if you want to utilize it in this manner, i'd recommend it.