I currently have 2 wet-dry vacs. One is a Shop-Vac 10 gal. drywall vac that I've had for about 7 years. It's an industrial model that I paid over $100 for, and I like it very well. The other is a 16 gal. Craftsman, that I only use for wet pickup, as I found after purchasing it that there were NO filter bags available for it! Otherwise, it's OK. I had another Shop-Vac that I think was 12 gal., but I gave it to my neighbor when they had a flood, since it wasn't all that great.
Shop-Vac has 2 lines of equipment - the cheap home models, and the better constructed and more expensive commercial models.
Nilfisk is another brand you might consider. I don't have the wet-dry, but I do have one of their HEPA vacs I use inside, and like it real well. They are also sold under the Clarke brand. Expect to spend some money for one of these.