Should I Use Oil or Latex Paint?
Oil-based paint (aka alkyd) is used much less frequently than in the past. Improvements in the durability of latex paints (aka acrylic), combined with their other qualities and convenience make them the most popular choice by far.
The fundamental difference between latex and oil paints is the use of different carriers and binders. The carrier is the liquid that evaporates, leaving behind a layer of binder and pigment. In latex paint the carrier is typically water with glycols or glycol ethers as a solvent. In oil-based paints, the carrier is a formulation of mineral spirits and petrochemical solvents.
The binder is the material that adheres to the painted surface. In water-based paints, it is formulated from acrylic resins, polyvinyl acetate and styrene butadiene. In oil-based products, binders include petroleum based alkyds, polyurethane's and silicones. Natural oils can be used, including linseed, tung and cottonseed oils.
Ease of Use
The award goes to...latex. The ease of clean-up with water is almost enough on its own to justify choosing latex for ease of use. In addition the ease of spreading and the low odor, make it easier to work with than oil.
Oil-based paint requires thinners to clean hands, spills, tools and brushes. The paint thinner then has to be disposed of in an appropriate manner. Oil paint is thick and sticky, requiring a little more effort to apply. Oil-based paints have a strong odor and the odor can last days or even weeks if you have a sensitive sniffer.
This has always been oil's strong point. It has a hard, durable finish. So hard in fact, it should not be painted over latex, because the softer coat beneath tends to flex and then crack the oil coat. Oil dries to a hard smooth finish and withstands abrasion well. Oil continues to dry over its entire lifetime, and eventually, if repeatedly recoated, will crack.
Latex however, is flexible and expands and contracts with the surface. Furthermore, latex's porosity allows moisture to escape from the painted surface (a good thing). As a result of improvements in the formulation of latex paints, their durability now rivals oil, or even exceeds it. Their are different qualities of latex and the best is pure acrylic. One hundred percent acrylic paint costs more, but it should last longer than cheaper varieties and ultimately save you money in the long run.
Latex-based paint is more resistant to fading, yellowing, cracking and chalking than oil paint. It resists mildew better and the best 100% acrylic paints resist abrasion. Most people can't tell the difference between oil and latex when they look at it, even professionals sometimes have to test the paint to be sure which it is.
In an unscientific test, I painted two wooden panels of beadboard. I used the same color, but I painted one with primer and oil and the other with primer and latex. I let them dry, and then compared them without knowing which panel was which. I preferred the oil painted panel because it had a warmer appearance. The texture of the paint was smooth and even like glass. It resembled powder-coated metal. The latex panel looked fine, but the surface was less smooth and did not have the warmth. Even though the same color was used, they were different paints and so the sheen may not have matched as closely. My observations of the two panels may have something to do with sheen rather than the paint itself. In any case, I used oil paint for the beadboard wainscoting in my bathroom.
Latex is faster drying. On the down side, it is not as effective at blocking stains from showing through. Latex is more temperature sensitive and has narrower acceptable conditions for applying paint. The biggest negative is that it does not adhere as well as oil paint. However, with proper surface preparation, adhesion should not be a problem.
Another point to consider, what kind of paint are you painting over? It is always safest to go over old paint with a fresh coat of the same type. It is generally considered acceptable to go over oil paint with latex, but proper surface prep is essential. In some rare cases, latex can actually pull multiple coats of old oil paint right off the wall.
Painting oil paint over latex is possible but inadvisable. The oil should adhere to the latex, but the flexibility of latex will ultimately lead to cracking of the oil paint.
It used to be that the binders in oil paint gave it the edge in durability. Nowadays, the binders in latex paint have caught up with or surpassed oil. In consideration of latex's other qualities, it now is the right choice in most cases. Many professionals will disagree and swear by oil-based paint. To be fair, it has some virtues, and in some cases may be the better choice. However, the debate may become irrelevant as oil-based paint becomes more and more legislated out of existence.