It's really hard to find good info on exactly what winch ratings mean. For the most part, what I've found is that a 5000lb winch won't lift 5000lb. It means that it will pull a 5000lb rolling vehicle up something like a 20% slope.
Does anyone know of where we can get accurate info on exactly what various winches are capable of doing?

Good question. There should be some law of physics, and equation that would help. The rolling part throws me.
There must be someone smarter than I am that knows the answer.

I'm not smarter than you, but a long time ago I figured out that one should have a winch that is rated at 1 1/2 or 2 times the weight of the truck you put it on. I found it saved using blocks and breaking cable...most of the time.

A winch is like a gun safe,buy bigger that you think. Lightman

It almost has more to do with the cable strength rating, and how much pull the winch can do with one winding on the drum.

Yes, you always need over capacity

I was told that the rating was at the hub. Each wrap decreases the rating by 8-10%. Most winches have 4 or 5 wraps.....

Buy the biggest SOB that will fit. Thank me later.