This is my opinion, no basis of actual fact and I have never ridden in your previous vehicles.
The Z-Car has alot of potential, but for me it is always a work in progress. When I first started racing autocross I was say 15 seconds behind the fastest car on the track in a minute course in a car with a lowering kit, upgraded shocks, and a cage. Now six years later there is rarely a car on the track that can get more than two or three seconds away from me. On an road track it will keep up with $100k porsches in tight technical sections (then get burned in the straight away).
But with the Z-Cars I think putting it as simple as buying suspension is underestimating how much work and research goes into making them handle well. I love Arizona Z-car products, I am just saying that a combination of suspension, wheel size/offset, tire choice, air pressure, front and rear camber/caster/toe working together instead of against is what makes them handle well.
The mentioned Arizona products provide stiffer components, better asthetics, less likely to rust or fail, easier and more adjustability, and are overall way cooler than stock stuff. Most importantly the brakes that come with that setup cannot even be compared to stock brakes. However you could come across someone that doesn't have any one of those products and their car might handle better than yours.
If you are looking for a project, a Z-Car will definately fill the shoes. Good Luck.