What a difference a change makes! I just went from 235/45zr17 Bridgestone RE730's to 215/55zr16 Kumhos. OK, that's 2 changes, from a 17" wheel back to 16", and from old RE730s to new ECSTA 712s. The Kumhos feel like a stickier compound. They grip better than the worn out tires but have more sidewall flex.

There is a performance tradeoff. While the car isn't as fast to respond to transient steering changes, the ability to soak up bumps allows me to actually travel faster over bad roads. I was able to run a rough road more aggressively than with the 17's, then took a sweeping downhill onramp about 3mph faster, again because the tires soaked up the bumps. The extra give of the higher sidewalls allowed me to raise my overall limit. Though they might not be as quick to respond, they do handle lateral forces well.

I would distinguish between autocrossing and daily driving. Autocrossing generally is on smoother surfaces, but in the real world, the suspension has to handle more variation. Someone recently wrote that European suspensions were soft but chassis tight. I think that might be the best compromise to make.