The biggest problem with very low mileage cars is that it often means the car's journeys have been so short that the engine and the oil are never warmed up properly. This increases engine wear, but it's not always the case as sometimes the car is just used for a longer trip once a month. If you can get an idea of how the cars have been used, then either could be a great buy.

As for Cat S cars, they are in that category because they have received structural damage in a serious accident. If it's a private seller you may be able to verify where the repairs have been carried out, but it's difficult to know for sure if the structural work underneath has been done to a high standard. Buyer beware!