I conducted a couple of non-scientific tests. I made 2 scarf joints with gorilla glue and 1 with yellow glue (Lepage Carpenter's glue - Titebond I equivalent)
All tests were done with maple to maple joints. The maple is either hard Rock Maple or Silver Leaf maple.
Conclusions:
1) All Gorilla glue joints failed at the glue line and only a couple of small snippets of wood were torn off. For these tests, I had hard rock maple to hard rock maple joints.
2) The yellow glue joint withstood the test where correct pressure was applied. The wood gave before the glue line. Where I had less pressure, the glue line failed. For this test, the wood that broke was Silver Leaf maple. Did the silver leaf maple break because it is not as strong as the hard rock maple? I don't know.
3) To break the joint, I had to stand on the neck portion of the glued up piece.
So why did the Gorilla joint not perform as well as Yellow glue in my tests? I don't know. I didn't take any more care in preparing the surface for one test vs the other. I cleaned and vacum'ed both surfaces before glue-up in all cases.
On my laminates prepared with Yellow glue, I noticed that the wood breaks near the joints and usually, there is a spot where the glue line is the point of failure and most spots (80%) are wood failure. I didn't try Gorilla glue laminates.
In the end, it takes a lot of force to break the joints regardless of the type of glue used but I think that I'll stick to Yellow Glue for now for all my laminates and scarf joints.
Just thought I'd share this with you.