Interesting..!!
Having both a very well sorted 3200 AC Auto and a 4200 CC, if I am honest they both have really good characteristics. The 3200 is manic when the turbo's spool up, but I suppose by then the 4200 has a slight head start, having slightly more power at the initial take off. Both interiors are excellent, both have good brakes, both have great roadholding and cornering ability. The 4200 (facelift) has excellent stability at any speed and if anything feels slightly better planted on the road at high speed than the 3200, only slightly. It depends on the year of each model I suppose and if you step up to a GS then it is a slightly unfair comparison. The later the car for each model, the better the performance is overall. I love driving both as they have differences which you can enjoy.
At the end of the day if you can drive well and quick, you will find a way to make any car sing an excellent tune.
I would have one as a daily car, no question.
Tis subject pops up every two months or so, ha ha.
After two years of owning a Gransport, i can only say the 3200GT is not a real contender, especially regarding handling.
But compared to an early 4200 ......i would defenitly go for good 3200GT.
Still: the exotic feel that my former black 3200GTA (tobacco interior) provided, can not be found that way in the later cars.
The boomerang-rearlightconversion on my GS did something for the exterior, but somehow the 3200's have something special, something hard to describe.
If i had the space to buy another 3200GT next to the GS, i would do so immediately, especially seeing that prices are bottoming out.
Go for a well maintained 3200GT now i would say!