After working for Sherwin Williams for 15 years, I have learned more about "paint" than most painting contractors learn in a lifetime.
With that being said, the quality grade of the paint YOU select and WHOM you select to apply it, is the most important decision in regards to repainting your home or business. Your painting contractor should be able to explain WHY this paint is better than that one, and the pros and cons of cheap paint versus expensive coatings. My mission, is to give you the property owner, all the options available, because my objective is to paint your business or home ONE TIME, with aspirations of gaining future business by referrals from you for years to come due to the quality of the finish on your home or business.
Your home or business, are your two biggest investments. The paint on the outside of your home or business is the 1st line of defense. Make sure your painter uses (what he says he is going to use) because if he doesn't, you will be paying much more, a whole lot sooner than you thought you would have to.