Hey folks,
Here is what I have found. About a year ago a friend of mine and I -- both longtime engineers -- made a test. We both had our opinions. He liked Gorilla glue, I liked good old yellow PVA woodworker's glue.
We set up identical tests and tested the strength. We both found that they both had, if properly applied, nearly the same strength. We found that the PVA was slightly stronger in our tests. And the strength variations due to application were greater with the Gorilla Glue. The difference was not enough to be statistically significant. The conclusion I have come to is:
PVA is the best for normal woodworking projects that do not need waterproof service. PVA is more forgiving in application (there is no special surface wetting and other concerns). Polyurethane (Gorilla Glue) can be used to attach materials that PVA cannot (metal, plastic, mirrors, etc). Polyurethane is better than even the type II PVA for wet applications. Gorilla Glue does not fill gaps (with any strength). Gorilla Glue is very, very messy and you absolutely need gloves or you will be wearing the stuff for days on your hands until the skin it is on wears off. Like most adhesives, they each have their place, but I think the PVA is much easier to work with and forgiving as long as you are working within its service parameters.
Eric