I've got both Kennel Club & Aviva. Haven't claimed and don't intend to
. The Kennel Club was specifically for my bitch who I intend to breed from, and they cover the breeding side of insurance for her.
It's like any insurance, you buy what you can afford for the best cover you can get.
Don't forget to get lifetime cover and ensure if you claim for a specific illness that will be ongoing, that the company will insure for that as an ongoing thing and not just for that year.