I had the weitecs on my mk2. So not an exact comparison. Went from a weitec fixed height kit to the coilovers. Ultimately I regretted it as I didn't want to go lower. Just thought coilovers were better.
I found on bumpy roads I was going slower from bouncing all over the place. They did get better with more use and broke in.
I can't see it being the bush myself. My mum had a mk1 TT. If anything it was more lardy than my mk4

There is a loose science in setting up coilovers, and the front end geometry. It was described to me on another forum. Something to do with scrub radius, rake. And piston travel matched with preload on the coil.
But basically if the wishbones are flat, it will corner and handle better than being wound down.
I'm by no means an expert, just played around a lot on my mk2 which was fully pollybushed. And I would never use Polly's as extensively again. Not fit coils that weren't fully damping adjustable.