Although all fuel filter perform essentially the same job, there are a lot of variations in specialty, and some designs are better than others. The biggest variation is in the type of materials used for the case and filter media, which has an impact on the filter's pressure capacity, flow capacity, what size of particulate it is able to filter and how often it will need to be back-flushed or changed.
The most visible difference between fuel filters is the outer case, which differs by the filter's purpose and location. The first fuel filters were serviceable units with a metal outer casing. This design was almost universally adopted by auto manufacturers, but most removed the serviceability of the filters, forcing the driver to replace the entire unit.
Aftermarket filters applied to older carbureted engines have included both plastic and glass, which gave the car's owner the ability to check filter condition without removing it. Most modern cars use outer cases made of stainless or galvanized steel, which is required as fuel-injected engines require much higher fuel pressures than carbureted engines.
Although most manufacturers sell cars with sealed fuel filters, serviceable units are still common on diesel vehicles like tractor-trailer rigs and construction equipment. Serviceable filters unbolt from one end and allow removal and replacement of its filter element. This is an important trait for diesels, as diesel fuel can thicken and gel under extremely cold conditions. Diesels also often require priming of the fuel filter if they've been run dry.
Three basic types of filter elements exist. The primary fuel filter on many vehicles use a cotton-gauze element, which flows well and does a good job of keeping large debris like rust scale, leaves and sticks from damaging the fuel pump.
The next in line is most often a crepe-paper filter, which uses an element folded back on itself many times over to increase filtering area. Paper filters can catch smaller debris better than cotton gauze filters but still flow well and take a long time to clog. It is for this reason that most cars have a paper filter installed somewhere in between the fuel pump and engine.
Very fine nylon screen filters were at one time considered only suitable as a secondary filter (placed in line after the primary filter) but are becoming more popular in the automotive segment as primaries. One traditional drawback of nylon screen filters is that they require frequent back-flushing to remove built-up contaminants, but modern filters have built-in pressure circuits that will do this automatically. Most modern European cars come with either serviceable or non-serviceable nylon-screen filters.
