Thee 17"s stock height is 50 aspect ratio. Which is pretty tall for performance only use.
The 18" drops the aspect to a performance friendly 40.
The other side of the positive for the 50 aspect is damage control. A 50 aspect tire can take a LOT more punishment that a 40 aspect tire.
So if you plan on any rough course, better to stick with a tire less likely to fail due to hitting any rocks, potholes etc at speed.
If you go with the 17 and 50 aspect ratio, then find tires with stiff sidewalls, instead of the current fad of total 'soft' mush sidewalls.
The stiffer sidewalls will give the turning power of the 40's in a 50 aspect ratio.
The OEMB.F. Goodrich tires for the Contor SVT had some of the stiffest sidewalls ever, and were fabulous tires for any sporting as far as cornering went.
Though they were noisy as can be on the street.