The Microtex at Wal*Mart is advertised as over 6.5 square feet and it is the largest MF I have seen/used.
Maybe it's because of what I started with, but the 16" x 16" towels are still my favorites. When folded in 1/4's, they seem to be just the right size for removing polish, wax or QD's. When you stop and think about it, the 16x16 gives you 8 wiping surfaces, each about 8" x 8". That's plenty for me to remove product from a vehicle.
I do have some WW, some larger plush, and the Wal*Mart giant as well as the 16 x 16 and I just use whatever is handy. I haven't been all that impressed with the WW for drying. They really don't seem much/any better than my regular MF towels. I still think I need to use at least 2 and sometimes 3 towels to get the vehicle dry.
I also use two when QDing. One to spread the QD, one to finish wiping the area completely dry.
While I didn't really care for the large Wal*Mart towels at first, I have been using them with S&W recently and they seem to be doing a pretty good job. I fold one into 1/8ths to make the first pass with the S&W, then do a finish pass with another MF to complete the job.
FWIW, I still use my cotton terry towels on windows, door jambs, underhood and trunk areas as well as for the wheels and wheel wells.
Charles