Don't base your decision solely on whether or not genetic conditions are covered. Take a look at the the complete package-what's covered, what it costs, the company's reputation for service, etc.
I have Pets Best Insurance (
www.petsbest.com) for my yorkie, and have been very happy with them. I haven't had to file many claims, but the ones I have were all covered, and I received the check in 4 days.