Deciding which paint to use has gotten much easier now that acrylic latexes have pushed oil-based paints almost to extinction. The acrylics offer superior performance (they don't harden with age, the way oils do, so they move and breathe without blistering), they don't mildew as readily, and they emit fewer VOCs, so they comply with new air-quality regulations. They also work over both oil- and water-based primers.
Hello, I have a sad situation to share -- a friend of mine who is a very good painter, experienced too, fell off a tall ladder that did not have "boots" on it. (I've never seen those.) Anyway, do you think he should have asked for boots before painting? Possibly it was a situation where he was shy to ask because he wanted the job... (I don't know all the details.)
I used to work at Sherwin Williams. The best thing to do is specify that you will purchase your own paint. If the painter objects strenuously, he was plaanning on making money in the ways this article outlines. You might pay a few dollars more for paint, but you will have control of the quality of what goes on your walls. Never skimp on paint quality.