The AW11 was in ways superior to the SW20 in its handling. There was alot of hype about the snap oversteer and the tendancy to face the wrong way, but this was from people that cant drive. The MR layout gave it perfect balance and amazing grip, only the lead-footed would complain.
Admittedly the first generation of SW20 turbos were vicious but still, respect the car and it flies.
There is no mechanical difference between a Rev3-5 SW20, only cosmetic.
My dad owned the non turbo SW20 (92) and it lost many powerful and even 4WD sports cars round the twisties. Whilst waiting for his 95 Turbo to arrive from Japan, he was borrowing an AW11 for a few months. The handling was close to that of a Caterham, although it was slightly underpowered in its stock form.
The SW20 Turbo he now owns (Rev3) is a pure beast, and if anything, slightly over powered for such a small car.
The only way an MR2, especially AW11, can be said to handle badly is if the person behind the wheel is scared to push it harder. Or, the car is faulty
The MR layout (NSX etc) may not be popular in production, but thats because it is impractical, and hard to drive well. The benefits are obvious though, and the MR layout is used widely in motorsport.
Although id rather work on a FR car!