The one thing I don't like about those break barrel rifles/shotguns with switch-able barrels, is they're usually only one shot. Most of the time that's fine, but having a quick follow-up shot at the ready can mean the difference between putting food on the table or just wasting a day.

The same idea follows if you are planning on using it for defense from animals (or people). On a break action, you might only get one or two shots out if you're lucky, and it's easy to fumble reloading. Even on an internal magazine bolt-action rifle, it's fast and easy to get four or five shots out. On a pump shotgun, you can get even more with an extended tube. It might give you more of a chance.

A single shot break action rifle/shotgun may be plenty most of the time, but then again, it might not be. Your level of comfort determines what you're willing to carry. I, personally, just wouldn't be comfortable with a single shot break action gun as my only firearm. I want at least two shots before taking the time to reload.

Again, that's just my opinion.