Being lucky enough to have both a 3200GT (two in fact, the blue and the white AC, hum) and a gransport (the blue US MCV who was for sale on ebay for a full year), I can give my humble opinion.
About the 3200GT and the unreliability, I know I'm a little bit biased, but it's not as bad as people think.
Today, we know the common problems and we have solutions, often better than original. It's even possible today to interpret the error codes.
If your not too bad with a spanner, you can do about everything yourself, it's not that hard.
In 2019 and 2020, we had an european gathering for the anniversary (In Bade Wurtemberg and in Burgundy), and most of the participants did more than 1000 miles during the WE to participate.
Outrun is right when he say the 3200gt is a modern classic, and this model have (at least for me) a special place in the maserati history (last of his kind etc...).
And you can't forget the boomerangs.
About the 4200gt, you have to live with the cost of the CC. If the gearbox of the manual is the same as the one of the 3200, it's not ecstasy neither, I even think I prefer the CC.
The problem with the 4200 (to me at least, I agree to disagree of course) is that the model sits uncomfortably between the 3200gt and the gransport.
About the gransport (the MCV at least, but it's probably not so different for the "simple" GS), even if the shape is very semblable, on the road, it's a completely different car. More focused, more precise, less GT, less beautiful, nicer sound. Still a very analogue car.
Well, you need to buy both
Ok, I know it doesn't help.
So buy a 3200 !