I'm considering those two, based on info I have. Pets Best sounds good, but it's not available in my state. There are pluses and minuses to all of them. Does anyone have any bad experience with a particular one? My dog is 7 and healthy, but I don't want to take chances.

I've never heard of either one of those.
However, the reasearch I have done shows the top two animal insurance carriers as
VPI (Vet Pet Insurance)
AKC (American Kennel Club) - it insures both pure and mixed breed animals.

I have three dogs on VPI (800-USA PETS) and find that it pays for itself each year. VPI also insures, cats, rabbits, birds and exotics (reptiles, etc)

Whichever one is going to cover more for the money is what I'd go with. I personally do not have any kind of insurance on my dogs but I have a very reasonable vet and extremely healthy (knock on wood) dogs. Research and ask a lot of questions about each plan to determine what they each cover for what they charge and ask your vet approximately how much it would cost to cover certain things you are concerned about-it may not be economically sound to get the insurance but better yet to stick a certain amount aside from each check to help cover costs for things that may or may not come up concerning the health of your dog.