Then again, even with a good door, you'd have to spend a lot re-inforcing the walls to get the same level of "protection" as even the cheapest rsc.
I think that the point is that most smash-n-grab types won't even both to try - they will encounter the locked door as an obstacle and move along. They're looking to ransack for easily portable and easily sold/traded items, and they're looking to get in/out with a minimum of fuss.
I know of two folk that have been recently burglared. The first, a friend of my wife, had her place (a nice middle-class neighborhood in Carrollton, TX) burglared during the day. The burglars kicked in the front door, went to the master bedroom, and proceeded to ransack the dressers, nightstands, and bathroom. They took costume jewelry, prescription meds, and small, easily portable items of modest value. They made no effort to get into the locked cedar chest or other similar enclosures. They left the large TVs and even left the game console.
In the second incident, a cowworker had his house burglared during the daytime in a modest neighborhood in Garland, TX. They kicked in the back door, went to the master bedroom, and ransacked the dressers, nightstands and bathroom. They took his porn, his prescription meds, his game console (but not the TV) and his mad money stash in the nightstand. They made no effort to take more than could be easily found in a purposed search and that could fit into a pillowcase.
If nothing else, these two incidents point to a similar MO - smash in, go to where folk are most likely to hide their smallest and most valuable things, and take only those things that can be carried away and have valid street value within a specific demographic. Given this - yes, a closet or similar with a outward opening door and a deadbolt or similar would likely prove as adequate a theft deterrent as would an RSC.
Oh, and in both cases the burglars searched every room for computers but did not take them - they draped blankets over them. In other words, they have been doing this long enough to worry about web cams catching them in the act.
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ETA - lining a closet in plywood goes a long way towards stopping folk from kicking their way in. Picking an interior closet, preferably one that backs up against an interior dead space with plumbing or similar, is even mo' better.