6.
IMO, most DA polishers should come with 2 speeds. low and high. Something like speed 3 and 6. And then the on/off switch.
setting 1 and 2 are pretty useless, 3 to 4 is good for waxing. and 4 to 6 is good for correction.
The nice thing about the GG6 is that speed 6 is very well balanced on the machine unlike the Porter Cable. With the porter cable I couldnt ever use speed 6 for longer than 15 minutes before my hand went numb, so most settle for speed 5 on that machine.