Between the two I've gotta say it depends on what your other monsters have.
Do the others add to five or more SBR? If not, G/L simply because if you're not entirely immune you WILL get screwed over eventually for an imperfect skillbind resistance.
If above is true, do you have a skillboost deficit? If so, heavily consider G/L since he has one and G/G does not.
Otherwise, G/G demolishes the G/L form due to the Dragon and Devil Killer awakenings. G/L's HP is alos preeeetty bad.