I used to own a 655CE ...loved it! Taylor 12s and jumbo bods are a natch together. But that said, I have to go with the GS as my preference. I've never heard a GS-bodied 12, so perhaps my comparo is skewed a bit, but my RT-12 is a GS body and it has all that my 655 had, and more (granted some of that "more" is likely due to other circumstances regarding build). The GS seems to have all Jumbo "thing" covered, but with the added benefit of being more comfortable. Were I choosing between a jumbo and GS in 6 string, for example, the the GS would get the nod. For a 12, all else being equal, I think I'd do the same.
Edward