Much better, in some ways, than a cigar box. The downside is that it's easier to hide a cigar box. A fire safe will prevent theft by the 'dash and grab' crew but against a determined thief with a smattering of time, not so much.
At my local safe company, they have a display of a Sentry fire safe ripped apart with a roofing hatchet. The construction consists of two thin layers of steel encasing about two inches of concrete. It's the concrete that gets the fire rating - the steel is just a cover. Might as well be plastic. If you can chop a hole in a hunk of corrugated iron, you can chop a hole in most fire safes - the steel isn't much thicker.
I think the most fire and theft resistant safe for the home is the round kind that fits inside the floor. To install it, you rent a 8" or 10" or whatever concrete hole saw for the day, cut out a plug from your foundation, lower the safe and add some cement.
Such as safe won't burn, you can't reach the recessed knob with a tool, and it's REAL easy to conceal. I've got one in a closet, a bit of floor tile covers the section containing the hole, and some nasty-looking underwear - complete with brown stains - covers the tile.
Security safes are "T" rated: T10, T15, T50. This used to refer to the number of thousands of dollars an insurance company would go for and was directly related to how much trouble it would take a thief to crack the sucker. What with inflation, I don't think the numbers refer, any more, to actual money.