My only goal is to deter smash and grab burglaries. Do not suggest that I buy a $2k plus safe. It's not going to happen.

I found a 24 gun cheapo safe locally for 400. I also found, locally, a simple security cabinet. The safe is obviously not overly sturdy, but moreso than the locker.

Given that I don't have priceless antiques would I be better off with the cabinet and reinforcing the door to the closet it'll sit in or am I better off with the dubious off brand "safe".

When I say reinforce the closet door, my idea on that is to use hinges with non removable pins, opens outward, grade 1 lockset, and reframe it with a steel frame.

Again, not trying to stop pros (which a cheap safe won't do anyway). Trying to deter 5 minute smash and grabs.

Which one is heavier and has better "retention" for the door and cabinet body (cross-bolts in the door and bolt-down points for the body)?

Given your specs, these would be my deciding factors, in addition to any fire rating.