It seems like the upgrade from 11ga to 7ga steel in the Liberty body is a pretty big difference
It sounds impressive, but let's throw some numbers out there.
7 gauge steel is .1793" thick. The AMSEC uses an 11 gauge (.1196")outer wall with either a 14 gauge (.0747") or 16 gauge (.0598") inner wall depending on model/year. Going with the thinner 16 gauge wall, you have a cumulative thickness of .1794", which is actually more steel than the Liberty by .0001".
As far as the door, the AMSEC has .5000" solid plate door, not counting hard plate. The Liberty is using .1793" for it's outer skin, with a .2500" inner plate for a total of .4293".
Hard plate doesn't do much to slow your average burglar, because most of them aren't drilling safes. I can drill through Liberty's ball bearing plate just as fast as I can drill through AMSEC's hardened steel plate. In this case I'll call it a draw.
The AMSEC has more steel in the body, and more steel in the door. In addition to the steel, the AMSEC uses a cast insulation which provides structural reinforcement (burglary resistance) and real fire protection. Gypsum board provides no structural reinforcement, and limited fire protection.
Door bolts can be an interesting discussion. Most people don't know that the the part of the door that holds the bolts is more important than the bolts themselves. Of course that's a whole other discussion.
Door bolts are important only when the door or frame are at risk of flexing. Assuming you have two solid surfaces, even a single small bolt would hold a door shut. Even small 1/2" diameter bolts would have individual shear strength into the thousands of pounds each. The bolt guides, door, or door frame of a gun safe would give way long before a bolt would sheer.
This is why is is more important to have additional bolts on safes with a higher risk of flexing (lighter strength doors and bodies). The bolts on the AMSEC and the Liberty are both sufficient to prevent a pry attack using common hand tools for a reasonable amount of time.