I'd go for the 3rd layer of WG. If you think about it. Putting #16 on is an irreversable process. You can put on #16 anytime but once it's done... it's done.
I have yet to see any benefit going beyond 2-3 coats of any product. If two look good to you, I doubt a 3rd layer is going to make an appreciable difference. Go with #16 over a section of your car and if you like the look, keep going.