during summer monthes, i hand wash my car couple of times.
for machine washes,
I find Petro Canada's machine wash with rotating clothes to be most effective, BUT most damaging to the paint as well.
after their wash, my car is sparkling, but my paint also swirly as heck.
if you go to esso or shell's auto pressure wash, the result isn't as clean, but much less damage can be seen on waxed surfaces.. ..probably washes off the wax though.