From what I saw from my direct experience (my former Mk1 compared to my current Mk2 manual), the first impression was that the Mk2 is more rigid (everyone already knows that, of course), giving also a first impression of driving a wider and more stable car.
By initially driving it like I drove my Mk1, it gave way to a more pronounced understeer, and it looked like being more "filtered" in its behavior, and with less feeling about what the tires are actually doing.
The Mk1 looked more "spirited" and direct in its feeling on steering and overall balance.
This is the first impressions I had, and I admit I was quite intimidated by the Mk2 initially, being a bit more afraid with pushing it into curves, since I couldn't get a clear feel about how the tires and chassis were reacting to my Mk1-like inputs.
After some more miles on the clock, I have to say that to me, Mk1 and Mk2 look like being much less different than it looked initially.
The "spirited" behavior of the Mk1 is still there, even if a bit hidden beneath a layer of overall rigidity of the chassis.
Hence, the more pronounced understeer I got initially, gradually went away, and by driving it with more confidence, and by throwing the car a bit more strongly into the curves, it finally reveals its "Mk1" nature.
Now I can tell that with the Mk2 I can keep a bit higher speeds in curves than it was with the Mk1, but it took quite a while to get there.
Of course. just my two cents, as usual...