Most people who say 17s are crap ruin handling etc have Never driven one on them so how do they know !!
flol AT THE CLIOSPORT SHEEP !
Mmm no, we're actually using well established engineering principles & equations used all the time in designing everything from designing the big/soft/comfortable Laguna to the S1600 spec Clios. Backed up by what proffesional racing/test drivers tell their engineers.
You can read a book about suspension so I'll just give one example. 17s often feel better in corners. This is 100% true, they do give better feedback and a more immediate steering response. This is good. However this is outweighed by the adverse affects that often result in LESS grip. Even though they feel better, they actually have less grip therefore you can't corner as fast. This is factual and not opinion based and, as said, can be backed up by pages of physics and equations.
Handling is about the perfect compromise. For racing or bigger cars that compromise can, and in many cases does, mean 17" wheels. Not in road/track-day clios though.
/education & listening to proffesionals.
Just as important as all of that however is this:
you modify your car for fun, looks & a hobby, not to increase apex speed by 1.37 mph on the ring road roundabouts.
Do whatever you like.