In tension, I think the G10 is stronger. In compression, the Ti.
But I agree with AllenC. Either is strong enough for a handle if made correctly. Either could be made incorrectly and make a poor handle, though I've never seen one. Think I read a thread in which a couple of folks were talking about a Spyderco Military with unlined carbon fiber handles (carbon fiber is cousin to G10) where the handles were a little too thin and didn't feel quite as solid as one might want.
outlaw918692000 is also correct. G10 is often combined with Ti liners. It is also sometimes combined with steel liners. It is less frequently used alone.
A well designed G10 handle should be as solid as a Ti handle. But it's as much a function of design as of the material.