For me Brian's question is very good but will not hold water in 25 or so years since the GT and PX will be both considered classics (matic or manual). No offense Bri.
My answer to the question though, is pareho lang sila.
In my opinion, the lines of the GT200, save the spaceship looking handlebar and modern rear rack, are classic vespa lines. We see it as a modern shaped vespa pero look at the uncanny legshield and the profile. Classic na classic na vespa!
Baka ito yung model in 50 years na sasabihin ng apo natin na "GT! ...vintage vespa ng lolo ko yan! That was sought after by guys who knew what they wanted ahead of their time back then...." Bla Etc Bla
Is it not we say that now about the GS and other vespa/lambretta old models we see now? They were advance scooters in their time.
I think the GT represents the 'now' of vespa world. The PX too, but the GT looks and feels like the best new thing that came out of the scootering market. And I am glad to be a part of this new era.

I adore those fully restored vintage scoots we see on the roads now. I sometimes wonder who was the first owner of that cool scoot, why did he choose that model, what was he like, tumatambay kaya sya sa Metrowalk? hihihi …But seriously, us 'now', with our GT's and PX's, we and our scoots are apart of this current scootering moment! The era where autamatic and manual vespa's are seen differently but actually are kind of the same.
In other words, I see the PX and GT are one and the same in shape and form and only differ in terms of the engine configuration.
I like them both. If fact I like them all. From the 40's to the millennium. I love all vespas. Second to only sailing though

cheers
edmund