The terms "latex" and "water-based" refer to a single type of water-based paint products, including primer and paint. This means that the base of latex paint or primer is water-soluble. In addition to water-based primer, there are oil- and shellac-based primers, both of which have bases that do not dissolve in water. Each type of primer has different advantages and appropriate uses.
Water-based primers are the most convenient to use. Generally, water-based primers are the least expensive option, and they are also the easiest to paint with. Compared to oil- and shellac-based primers, water-based primers create less of an odor, and they dry faster. Since the base is water-soluble, the primer or paint is easy to clean up with water and soap.
Oil-based primers require a special brush to apply and are more difficult to apply evenly to a surface compared with water-based primers. They also take longer to dry and produce a stronger odor. However, oil-based primers bond more strongly to surfaces and therefore last longer. Since oil is insoluble in water, soap and water often can't be used to clean stains off oil-based primer surfaces. However, since oil-based primers are tougher, you can scrub them much harder, allowing you to clean off tough stains such as ink without marring the finish.
Shellac-based primers use a type of resin as a base, which makes the primer very thick and tough once it's dry. For this reason, shellac-based primers are best suited for outdoor surfaces such as decks and picnic tables, as the resin base will allow the primer to withstand the elements. Shellac-based primers adhere well to slick surfaces such as smooth wood, metal and glass.
Choosing a Primer
Consider the surface you are painting to decide which type of primer and paint to use. For large interior surfaces such as walls and ceilings, a water-based primer is most convenient. However, if you plan to paint over the primer, choose an oil-based primer, as it will have a stronger bond with the (oil-based) paint you apply. Oil-based primers are better suited for surfaces that experience contact and abuse, such as woodworking and cabinets, as water-based primers are more inclined to chip off these surfaces. Shellac-based primers are best for use on outdoor surfaces or indoor surfaces that require maximum protection or sealant.