If all things are equal, the G2 and the Gold Bug Pro give off the same signals to good targets in, around, under trash. The audio on the GB is sharp, and does not false from what I can tell. My tests have shown that the GB can pick out good targets next to iron and even under the iron / trash.
Today I found a quarter that was under a pull tab, the pull tab was seen in the 60's VDI range and the quarter screamed at me with a higher / louder tone with a VDI of 87 / 88 on the VDI. All this was in DISC mode with gain at 80, DISC at 40 and ground balanced in the 60's. The pull tab was 5" down, the coin was an inch deeper. Oh, and I was using the F5 stock coil on my GB. The VDI was jumping all over the place from 62 - 88, with the 87 / 88 reading the tone / audio stood out, so I knew there was a good coin or a possible silver ring there.
I have not had the chance to use a G2, but based on what I have seen and read, and based on the fact that the G2 is really a Gold Bug both detectors should have the same characteristics and perform the same way. Even with the ID numbers, 88 for a quarter, 58 for a nickel, 82 / 83 for a penny / dime.
I guess I need to get a G2 to confirm all this, unless someone has both detectors and can pipe in here.