In the end, I decided to go with Kumho's, because the dealer said these tires are really good, even though they are much cheaper then the rest of the tires (got them 70€/tire). At first, I must admit, I was a bit concerned. The grip was ... strange ... especially on wet roads. They were good on dry road, but in the wet, especially on the highway, I had no feeling, what is going on, it was almost like I was floating but there was no aquaplaning since the car was not sliding or losing grip. Really hard to explain. Then I checked different pressure values and found out that when inflated on 2.6 or higher, the tire becomes completely different. And the feel on the steering wheel, even on Prius, which has a very numb steering wheel feeling, became something completely different. Maybe tires needed more time to "run-in" than usual, but now, after cca. 3000 km on them, I am really satisfied.
I just returned from a trip to Tuscany, after some 1500 km on the typical windy roads, there was no problem. Even with some spirited driving, grip was great, feel was great. Yes, Prius really is not a car that "likes" windy country roads, it is great in city, great on highways, well with these tires, it does not oversteer so much any more and it is fun to drive also on country roads.
A part of the return trip from Tuscany also included driving on really wet roads and the feeling was there, no aquaplaning even on harder breaking. I guess these tires just need a bit more time to run in and a bit higher inflation pressure.

same kumho problem... balancing & egg shape. 245/45/18 100Y XL
I've always used kumho because the price well reflects in proformance if only they didn't need constant rebalencing.
I've had 4 duff pairs, ku31 x 2 pair, ku 39 x 2 pair that had to come off in the end they were so bad.
No amount of balencing can sort an egg shape tyre.
These new ps71 are very soft, squishy, feel like running on 20psi with 30g wheel wobble even after twice rebalencing them & 1 of them is egg shape.
I am worn out with trying to get them right & think after years of kumho on various different cars I'm giving up on them.
Changing to Dunlop.
I always feel bad going back to the shop to moan they must think it's me lol but kumho have let themselves down & I will say so.
PS71 is more expensive, lower spec & lower quality, not for me, I like a tyre to be not thought about coz it's getting on with it's job instead of feeling there's a 60mph side wind blowing me around & the steering wheel hammering out of ny hands not to mention the amount spent on rebalencing & hanging around tyre shop waiting for my turn.