I've been around nothing but the SOHCs and have never had any experience with adjustable cam gears.

I've read many books on performance, but do to a lack of $$$ the best I did was a homemade turbo kit.

That said:
Degreeing cams should be done on a dyno.

What is the maximum expected gain out of Adj. cam gears?

I feel that it helps the DOHC more than the SOHC