My experience came from the following cases:
Case 1. My garage's boss, driving a 205GTi himself, had some 306 owners
upgraded their wheels to high performance low profile ones and left the
original 306 wheels there. Those wheels got fitted on the 205 without any
problems.
Case 2. I ran over a stone on freeway and cracked one of the alloys. With
that I no longer carries a standard 405 Mi16 alloy as spare. Instead, I
have a 205GTi alloy as spare from my garage's boss.
I also like the Peugeot alloys very much and I think they are the best
manufacturer fitted alloys. However, they're also very expensive from the
sole HK dealer and are nearly two to three times more expensive than other
brands. Unless I'm as lucky as my garage's boss, I'd just stick with my
original alloys for now and may be re-paint them at a later time.
Lewis To, '89 405 Mi16, Hong Kong.