Take you pick of forged lowers, there are many. Bushmaster, Aderson, Palmentto and on and on. All are Mil-Spec. Billet is a whole different story, most are quality lowers. With the billet comes the visual aspect, they are machines in many different way. Some are blocky with sharper, right angles and such and some or more flowing more "Polished" so to say. You will be good to go with most "Forged" lowers and take your pick of the billet lowers. Depending on what visually works for you.
Mega Arms does some good looking billet stuff but there are many to choose from.