What are the pros and cons of different manufacturers? I know Black Rain uses solid aluminum billet machine milled rather than forged for the lowers which, in theory, makes them stronger and lighter.
Weight and strength advantage go to the forged part. To achieve the same strength in a billet part it needs to be thicker. Billet can be stronger but requires additional material.
Billet has the advantage of having custom features. Ambi controls, 45* selectors, flared mag wells, just a few of the different things found with a billet part.