There are two advantages to using a trust, one is you don't need a LEO signature on the Form 4, this can be important if you live in an area where the Chief LEO will not sign off. The other advantage is that a trust, like a corporation, may have multiple 'responsible parties'. This means if you have family members, etc, who might want/need to have access to the NFA item without you being present, you can include them in the trust and they can legally have possession of that item.
The down side of the trust is the cost involved in establishing a good and proper legal trust. The ATF is working on rules that would require trust members each be fingerprinted, have the background check and LEO signoff, which would eliminate reason one for the trust. If they do establish such rules, existing trust transferees can expect to be getting ATF letters that would get the trust paperwork updated with the FP cards and background checks. This may or may not happen, but I expect it will at some point.
If you transfer to an individual, no other person can have access to the NFA item without you being present. This means you need it to be locked up in an area that only YOU have the key/combination, not your wife, sister, son, etc.
Other can use the NFA item if you are present, they just can't take it to the range without you.
NFA items in an estate transfer tax free on a Form 5 to any legal heir, documenting this in the will is nice, but not required.
I'm a Class II mfg, and I've been doing Class III since they had 4 digit ID numbers, so feel free to ask any other questions.