I did some research on this after losing 10 UPB switches which was not even during a storm or anything apparent. First, some experts feel that some of the ratings given such as Joules is meaningless (see
this post).
They also say if your wires are longer than just a few inches then you are diminishing the effectiveness of the unit. The best whole house protector is one that fits behind your meter, it has essentially no wire leads and protects the point of entrance. Some utilities will sell them to you, some rent them. While renting costs more, you do have the benefit of the utility maintaining it and replacing it if it ever goes bad. Next best would be a unit in a NEMA-3R enclosure at the service entrance. Last choice would be a unit by your main panel. If you only do your panel, SquareD makes a circuit breaker replacement that eliminates the wire leads. It is important to wire it in as close to the service entry as possible, so in a breaker panel, it should be near the top.
As far as warranties, the ones that do come with them have more holes than swiss cheese with all kinds of requirements and outs for them. And then then usually only cover 'white goods' which is major appliances like kitchen stuff, not electronic switches and devices.
Anything with a plug should also have a local surge suppressor in addition to the whole house.
Also, many, if not most surges actually come from WITHIN your own house from devices with motors like your AC, Fridge, Dishwasher and Vacuums. These surges build up over time and act as 'electronic rust' and slowly degrade your sensitive electronics, hence the need for local suppressor where you can. Of course these do no good for wired in switches.
Bottom line, do the best you can but nothing is perfect.
