Presumably a well engineered product would have substantial margin. I would expect 20-50%.
That being said if the 7000 pound version is only a couple of hundred more I personally would spend the extra money.
Don
I was just going to touch on that myself. The lower LB rating would be fine for any hobby cars I have but I decided to spend a few more $ and get the model that can handle everything I'll conceivably own. When it's time to do any work on my truck I'm glad I did.