Racoons are the worst! They will find a way in, somehow, and will only give up when they are buried in your garden with several ounces of lead in them. When they show up, bad things always happen.
Bears, however, will tear up your chicken tractor like paper, if they get a mind to. Thankfully, however, they usually do not cause too many problems.
The only "good" thing (and I use the term loosely) is that raccoons are or should be night time only predators . Hawks attack during the day (Thankfully they are not the most efficient predator) and foxes can be out all hours of the day or night which makes them the worst in my book, plus they are next to impossible to catch or put a stop to.