I was bitching about the handling when I went from 17'' to 16'', I can't image how big of a difference u feel.
With the regular Mazda 3 GTs (2.3L), I went from 17'' RS-As, to 16'' Gislaved Nord*Frost5, and the handle was noticable shittier (in the dry).
However, at temperatures below 10 degrees...