I have ridden bikes with 650c wheels, 26" (mtb) wheels, 24" in front/700c in back (Terry), and 20" (Bike Friday), and they all seemed plenty responsive to me. No really huge differences (other than the stability of a huge mtb knobby, of course!)

I must say, tho, I totally looooooooove all those pretty Sillgeys in ice cream colors! I have never seen one. Totally cool!