You received a lot of recommendations to buy big capacity, but those safes are very difficult to move. Since I bought a "security cabinet" about six months ago, I've already moved it to a different room. Moving a larger safe up or down stairs, or to a new house is not a trivial task. Instead of buying big, consider buying quantity.
FWIW, I declined the gypsum drywall-lined RSC's and just went with a Stack-On cabinet. It's just a 14 ga sheet metal cabinet with welded seams (spot welded). It has a 3-point latch and a piano hinge on the door. It was $129 for an "18 gun" cabinet, and I could buy a half-dozen of them for the same money as an entry-level Liberty with better pry-resistance, but the same thickness steel that easily zips open with a battery-powered tool. The drywall-lined RSC's give the illusion of being more solid and secure because the drywall stiffens the thin sheet steel.
Right now I only need one cabinet, but I would rather have several of these than a larger, heavier RSC that I could never move by myself.
I believe the RSC's do offer substantially more security, but only when you pay for it. An 11 gauge steel RSC with 15 locking bars and a "90 minute" fire rating is slightly more secure, but will cost well over $2000. A 7 gauge steel RSC with a 2.5 hour fire rating is where you can really start to be confident that your assets are more secure than a 14 ga sheet metal cabinet, but it will set you back nearly $5000. If I had an RSC that costly and it was damaged, I'd lose more on the RSC than I would on the contents. But some people have a lot more than $5000 in guns. For them, I recommend insurance. If I was underwriting gun insurance, I wouldn't offer a discount unless the guns were stored in a real TL-30 rated safe.