Not with race tires or any other good performance street tire. The sidewalls are so stiff on those tires that they make up for it. Plus having more sidewall is good, to a limit, for autoxing. Basically it allows you to have the ability to adjust tire pressures to match what is going on with the car. The shorter the sidewall the less the tire pressure actually makes a difference. It is almost always true to run the smallest wheel you have at your disposal that will fit.

Another advantage to 15's is cheaper tires.

2004 Focus PZEV 2.3L - KW sport suspension, SP camber plates, Eibach front swaybar, FS intake, FS Stealth exhaust, 3.82 Final, Torsen ATB, Prothane MM insert, E1 CSVT wheels 1/4 mile - 15.201@89.4mph