Definitely Trust. It allows others to take possesion of your items if you wish. For example, i have to keep my first can locked away from my fiance when i'm not around. Also, it will make transfer to your offsrping, if you have or intend to have, much easier.
I did mine through TX Law Shield and they even provided me with a nifty card stating that i am the legal owner of NFA item(s). It has their phone number so that if i'm ever hassled by LE i will have legal assistance at the ready. Yes, it was more expenisve than other routes but i already use their other services and the associated legal protection was a huge bonus.