I've done a few hundred miles with the new tyres now, including a somewhat spirited drive this morning, so time for a quick appraisal. In short: they are great.
I have said in the past that I have not been all that happy with the stock Michelin PS4. They were not bad, but quite often there were situations where they didn't really inspire confidence. I cant quite put my finger on it, but I had a feeling like the car was up on it's toes all the time, as if the pressure were too high, or I was running Primacy tyres like the old GT. Lowering pressure to 32PSI helped a lot, as did an alignment, but I'd still get that niggling feeling sometimes while out for a drive, the car would feel a little light and not all that planted, sometimes even enough to make me abort a drive because I didn't trust the conditions.
That feeling seems to have gone now. I've just been out for a drive at 5.30AM, it was dry, clear and cold, about 5-6 degrees; no frost, but a bit of dew. Exactly the sort of autumnal conditions where I'd be second guessing the old tyres. With the new ones, I've had no such problem. The car feels much more sure footed to me. I intentionally took a route where I knew there'd be some quite tight turns which might usually make me very cautious, but the car felt more stable and planted through them. And that made the whole drive that much more enjoyable for me; I know some people like a car to move around a bit, but I'm much happier with that secure feeling of grip. As for moving from 215 to 225? If there has been any loss of precision or feel, I'm either not skilled enough, or not driving hard enough, to perceive it. And even if I could, the better grip makes up for it.
The ride is better. Bit less tyre roar, and I'm sure they soak up the little bumps and imperfections in the road better. Not night and day, but feels like it thumps less over road joints, tarmac patches, etc. And that is with the pressures at the stock 35PSI, and the new tyres have a higher load rating (92 XL, as opposed to 87 I think for the PS4, which I ran at 32PSI). Perhaps the higher load rating is why I can't really feel any loss of precision.
Other little plus points - I think the wheel looks better with less stretch and a more square sidewall, and should hopefully make the rims a bit less vulnerable to kerbs, especially as the Goodyear seems to have more chunky rim protection. My speedometer was always pretty accurate, overreading by 1-2MPH at most when compared with GPS....but the slight increase in diameter now means it is absolutely spot on perfect. Which is good for those of us with a little OCD.
Not sure if the improvements are down to switching from Michelin to Goodyear, as opposed to increased tyre size. As I said, the PS4 is in the same segment as the F1AS6 (albeit a generation older), so I didn't really expect a big performance gain. But moving to 225s gave me more options and cost less, so I'll be sticking with that for now.
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. Had some premium contact 6's (so that's the 4) on some older wheels so not brand new - also great tyre for feedback but didn't stand up to track. 
