[Ecky]

3 degrees likely won't amount to much, and whether advancing or retarding will benefit power or fuel economy will depend on where it started.

~

I only have personal tuning experience with intake cam VVT. Higher in the rev range, retarding tends to move peak torque upward in RPM, and advancing moves it down, but things get muddy below... say, 3500rpm. There, "it depends".

Most newer engines run a higher static compression ratio than can be readily (or efficiently) controlled by ignition timing alone. Sufficiently advancing or retarding cam timing effectively limits how much air gets into the cylinder, reducing the absolute peak cylinder pressure to a manageable number, while also allowing for very high expansion ratios. (as an aside, most companies choose to control this via retard, likely because it more reliably meters cylinder fill).

Tuning on Hondas is typically done in 10 degree increments, with ~50° total variation of the intake valve - and the full range is typically used under various driving conditions. Mazda's high compression engines have 74° of intake adjustment and 56° of exhaust adjustment (and a maximum of 92° overlap). 3° likely disappears into background noise. That said, I'd probably favor the more advanced position, without knowing anything else about the engine.