308 Brake conversion

[BiG K]

Would you really feel the difference in acceleration/turn in with 2kg + caliper weight more each front wheel?

You definitely feel the difference...but I prefer it. It feels more solid.

As in more planted and stable?
Noticed any difference in acceleration or not really noticeable? 308 setup would be great as newer caliper than 307, looking at 207/208/406/407 setups too.

This is just my opinion and even then, it's just what I feel and not what will translate into hard figures. It feels more planted and solid as like Ripp says, it feels like there's another passenger with you...but without the weight penalty of a passenger. Adding any weight to a car is going to slow it down but a few kilos is negligible at worst.

What happens is, there is a larger mass of steel spinning and a large mass of steel wants to spin true. So when you try to turn it off axis, it will resist that movement, resulting in more force needed to turn the steering wheel. I prefer that feel whereas I think Ripp prefers a light  chuckable feel, it all boils down to personal preference.

If you look at the big brake kits of today, you'll notice the calipers are nearly always monoblock design, whereas older multi piston calipers were a two piece design with bolts to hold it together. The older system had far more flex , which reduced efficiency. But the 308 is not a race car and ultimately there will be a tradeoff in price, so the 308 calipers may not be noticeably better.