I see no reason to go use a different grade for the gun bodies and grip frames. Certainly judging by the finish and matching of the parts on the Vapor I don't see any improvements.

The most important part of the cosmetic appearance of the gun is often the finishing of the part. How well it is polished or prepared. And then how well it is anodised. I have seen good and bad work with 6061. I have seen many guns in 6061 that are far better than the Vapor's I have seen so far.