This is my second MR2, as I had an AW-11 (1986) which I got rid of about 3 years ago.
The '91 Turbo is much larger inside and out, much better-looking, and much, much quicker.
The larger size has changed several facets of the MR2 "experience" from the older models. There is a lot more room in the cabin for passengers, which makes the car more comfortable, but tends to detract a bit from the go-kart feel so prevalent in the AW-11 car.
Despite being much larger, however, it seems to have less storage space. There is no more room behind the seats than there was in the older car and, due to the fact that the spare no longer sits flush against the firewall, the front trunk is virtually useless. My '86 routinely managed two of us, and our golf clubs, bags, and carts. I doubt that will be possible with my '91, but I haven't tried it yet.
The lack of more storage space, and a slightly less race-car feel are really the only things I can think of that the older car has over the newer one.
This car seems extremely reliable, something which cannot be said of my '86. Surprisingly to me, the car is still using its original timing belt and clutch, although the latter is getting a bit worn. Further, due to the Toyota's non-interference design, having the timing belt break means you have to be towed home and re-time the car with a new belt on it. Breaking the timing belt on most other cars means an awful noise, mashed valves, and many, many dollars to rebuild the top end.
My '91 is blisteringly quick, and very, very beautiful. The AW-11 was slow and boxy (but still a heap of fun). My car is signal yellow, and I can't go very far without it being stared at... not that people staring at my car bothers me ;).
I don't believe most people realize that they are staring at a nearly-13-year-old car, and many probably don't know they are looking at a Toyota.
The body is reminiscent of Ferraris of the same time period, and that is probably not a coincidence.
In fact, just yesterday a young gas station attendant came out of his kiosk as I pulled in to fill up and said, "Dude, that car is SICK!". I understand that sick means something along the lines of "very nice". That isn't the first time I have had a compliment about the car, of course. The important thing to note, however, is that the gas station attendant was manufactured around the same time as my MR2, demonstrating that the car has an enduring appeal, and does not look nearly it's age.