Both a great sealants. WGDGPS is pricy though when compared to a lot of the other sealants out there. I do use both myself, and I will try to describe the slight differences in each product.
The Wolfgang product has a lot going for it. I myself reach for it as a sealant for dark or mid tone colored cars. I find the WGDGPS is unlike a lot of other sealants in that its final look is more like a carnauba wax in the fact that it offers more jetting in the color field then most sealants do. By jetting, I mean it gives the paint color a more intense look and warmth that is normally reserved for a carnauba wax instead of the more sharp reflections that a typical sealant gives. This, doubled with its longevity (I have seen it go for at least 6 months in FL weather) makes it a fantastic alternative for your solid black or red car that you do not wish to wax every other month, and do not mind loosing some color depth used by a sealant.
It goes on fairly easily, with little effort, but you have to use a very small amount. I also find it has a slightly longer cure time then other sealants ( around 45 minutes.. of course depending on your environment) and of course, if you wish to top it with a wax, I let it stand overnight before this next step.
If the WGDGPS is more like a carnauba wax, then the Wet Diamond sealant is its opposite.
I find that on darker colors, the WD gives a more sharp look that really stands out. It can "feel" a bit colder on dark or mid tone colors, but the reflectivity and approach of the paint is more intense. The lines of the body stand out more, while the paint just looks like its ready to attack.
The application of the WD is similar to the WFDGPS in the amount you use, but the similarities stop there. It cures much faster, allowing you to remove it in about 15-30 minutes (once again depending on environment) and if you are going to be topping it with Midnight Sun (and if you have a red / orange / black pearlescent color, you should be... no questions asked) you only have to wait about 8 hours or so. Which makes it fantastic that you can apply the WD in the morning.. finish everything else up and later that day get your wax on.
In regards to dusting, I have not come across it on either sealant. If you are using the small amount you should be, it will not dust.
The cost factor is the major player here. For the same 16oz, you are looking at a $20 difference for the WGDGPS. Is it worth it?
For me, I like to have both on hand for the reason stated above. If I have a client who wants that length of protection, but does not care for the razor sharp look of a sealant, I will go with the Wolfgang.
If I get a car painted in a mid tone / dark pearlescent, you can bet it will get treated with WD. Nothing else comes close to this sealant for the look these paints deserve.
Now, to throw a wrench in the works.
With the release of CG's Blacklight, I find myself reaching for the WFDGPS far less. The backlight has the beautiful jetting factor, but with no effort to apply and top with (15 minutes cure time and about 1 hour wait to top!!!) and it being cheaper, (and smells wonderful I might add) it is the clear winner for the "carnauba effect" sealant.