what size for ultimate handerling?

[Humble]

I say go for the smallest diameter rim that will fit over your brakes. The biggest reason to do this is the cost of rubber. If you're looking at street testing that means a semi-slick at best and the smaller the rim the cheaper the tire. I went with a set of 18's to get maximum tire diameter and width (I couldn't find a 285/295 16") but my semi-slicks also cost me over $1600 after mounting and balancing (including a discount). A set of 205 or 225 15" semi-slicks would be half as much at most. There's also rotating mass and unsprung weight to consider, smaller rims are are much lighter and better at almost everything except top end speed where the smaller wheel diameter bites you in the ass.

In all honesty I would rather have a smaller diameter wheel with cheaper tires and better price/performance than larger more expensive wheels. If I could have used 15" rims I would have in a heart beat.