The threats that classic wood gun cabinets protect against are not burglary theft or any kind of determined thief.
They may protect against "honest" theft -- the opportunist who could just grab and scat. Or the person who doesn't want to damage anything or make noise while stealing.
But as far as protection against elements, rust, thieves and unlawful seizures, a safe does a much better job.
The problem, of course, is that when a thief sees a gun cabinet, he can see what's inside to steal. Most are not very sturdy with regards to theft prevention. When facing a safe, it might contain guns, a stamp/coin collection, or simply important documents.