Bigger wheels are obviously heavier. Heavier objects are harder to rotate which means reduced throttle response, and also it is a more burden to brakes. Also I think you lose some of the agility of this car.
I know it is just a marketing scheme but according to Enkei website; "Every pound of unsprung weight savings has the effect of reducing overall vehicle weight by 20lbs."
(
http://www.enkei.com/rpf1.shtml)
(And by the way, I didn't buy Enkei wheels so I am not trying to sell anything)
Plus this is just my personal opinion but 19s look too big for this car.