sole prop = several disadvantages, starting with more liability, plus your personal collection now becomes part of your FFL, and every gun you own is now subject to ATF review. Big advantage of sole prop is you get to keep non-MG NFA stuff you acquire if you have SOT, then give it up. You can keep it with LLC, but you have to keep paying your state every year to keep your LLC alive. Unless you have some big plans/other issues, the other options aren't really worth the trouble and expense.