Watching reviews, sounds like the 991.2 GT3 is a huge improvement over the .1. Gained back a lot of what the 991 lost from the 997. 991.1 GT3 never particularly appealed to me because of the (lack of) steering feel and PDK. Combined, I'd much rather have the 997. 991.2 looks to have addressed both.
The GT4... always feels too held back/gimped to me. I'd really like to drive one that was properly geared, to see if that addressed it.