You've already gotten some good responses but I want to toss in my two cents worth here. I've lived in Canada all my life and I've lived outdoors for large majority of it. I have hiked in the mountains, rafted, kayaked, cycled, camped and just put anything else you can think of in the outdoors. I can tell you I've done that in bear country and I have never had an issue. Now I'm not saying that you won't have an issue but I think if you prepare for all possibilities you're going to end up living inside of a nuclear hardened bunker. The biggest thing is to keep a clean campsite and camper (dump garbage as much as possible). Keep a can of beer spray or some beer bangers close by 24/7. Watch out for signs of any wildlife in the area. We have had bears walk through our campgrounds on many occasions and just ignore the people in tents and Rvs. In glacier National park one of the members of our party slept in a hammock and woke up in the middle of the night to find their hammock swinging back and forth and a grizzly underneath it walking away from them. There are lots of stories about the horrors of bears but honestly for what you would have to prepare for it just gets to the point of not being practical.
I myself currently use a van that I've camperized. But I've also used a motorhome and a truck camper. Never once have I felt any less safe in these then I do at home. Now if we want to talk about people that's another thing. I have moved more times because of problems with people then I ever have because of problems with animals. Yes a regular camper could be broken into by bears but honestly for all the people that camp and for the number of actual bear attacks it is extremely rare for this to happen.
Find yourself the type of unit that you want, that's going to work for you, and get out there and enjoy. I would be more concerned about repairability and comfort than any animals.
Thanks. I recognize the likelihood of a bear attack is relatively low and that there are a number of things I can do to reduce it further. These include using a bear fence, keeping a clean camp, staying away from bear cubs and feeding grounds, etc. And, even if a bear approaches, it might just be curious and not attack. I'm guessing these points can also be said for moose.
This said, an extra measure of safety might not necessarily be a bad thing. While I don't want to become paranoid and/or camp in fear, having a safer shelter to sleep in does provide some insurance in case of an attack.
I also want to be realistic about how well I will keep a clean camp. While I will do my best, there could be one or two times when I continue wearing in my camper the same clothing I wore when eating 100 yards away. Or, I might not realize that something in the camper is giving off an odor that attracts animals (could be toothpaste, deodorant, soap, etc.,).
Lastly, while I initially focused on a bear-resistant camper, I now realize it would be better for me to consider other animals, such as moose, muskoxen, wolves, cougars, etc., as well. It's also important for me to mention the possibility that I might camp alone.
Despite these comments, I want to continue to thank you and everyone else for your responses. These are all very important and help me better prepare.