Well, you seem to indicate your GM is too heavy. If that is truly the case, then the Infinity won't be any better for you. As for the question if Infinity is better than the STI GM, then I will say will 100% confidence, that the Infinity is a much better, full custom firearm. Better machining, better parts, custom choices made by the end user, and absolutely better QC. Now, what that costs you, vs. how well you shoot it is the question. I chose to go with Infinty and it has done nothing but help me.