I'm in the same boat as you, as my Maxima is Arctic Pearl White. I have tried Gold Class, #26, and #20 (and others not listed in this thread). Gold Class is so-so. It would suffice for non-Autopians, but we here tend to keep looking for what's better. #26 is a good wax, and it does look good on properly prepped white paint. But as we all know, there is always something better. #20 is easily my favorite on white, by far. It gives my paint a brightness the others just can't match. It also increase the reflectivity, giving a nice shimmering, wet look. I've topped it with #26 with the hopes of finding the elsuive "perfect shine", but honestly don't feel it did anything to increase the looks.
Generally, white is hard to make look good, but #20 does it very well. It won't give depth like can be achieved on dark colors with various sealants/topper combos, but it does make it look stunning for white.
An added benefit to #20 (beyond what GC and #26 do), is that my car stays clean. A good rain, and the car looks clean. Washing the car is a breeze. And using the "sheeting" method, drying is a snap, requiring only one towel. Tar literally washes off with a normal car wash. And bugs are easier to remove from my paint than on my Rain X'd windshield.
Application and removal of #20 is very easy, although it can be hard to tell on white where you have applied it. I've had no staining of trim problems, but I admit that I am careful.
Sorry this is so long, but I have to echo other's opinions that a sealant is great on light colors. #20 is by far the best "wax" or protectant I've used on my white car.
Others may have more informed opinions concerning other manufacturer's products, as I've only tried Meg's #20 as far as sealants go. But with the results I've achieved with it, I don't feel the need right now to try anything else. I can only guess that other sealants would give comparable results, and the choice would come down to personal preference of manufacturers (cost, availability, ease of use, etc...).
Dave