I don't believe there is a clear best here. Each have advantages and disadvantages. Flexwatt is not assembled so to some extent the ability of the person attaching the wires defines the quality and safety of the product. Cable is consistent to the manufacturer. I have used a number of brands and like the zoo med best of the ones I have tried. The cable is water resistant and this in some applications is a big advantage (RACKS!!!) It is fairly even heat wise and easy to work with. I do like flexwatt for the size of the heat area cable is a big trickier that way. I don't believe one is more prone to issues than the other. The blunt truth is neither should be trusted. All heating devises need to be routinely inspected and carefully checked over. I do all my heat elements at least twice a year and some more than this. The only other comment is a Canadian legal issue, if you are planning on being a business or are, flexwatt must be wired by an electrician under Canadian law. This makes flexwatt very very expensive. Failure, means no insurance, and criminal liability if anything goes wrong.