i've done this change several times on different cars. Just gives a little more grip really. No downsides, no less sidewall so it's no harsher, and 195/50/15 are so much cheaper
Your wallet will feel considerably heavier if you go for 195/50.
I know its a bit late for reply but will the 195/50/15 fit the dynamique alloys ok (came with 185/55/15 as standard)