Trading good texture work for "more brushes" is a cop-out =/ If anything, more brushes and less textures generally makes for a slower performing map. You can simulate a lot of visual depth with properly used, well selected textures. You are far better off learning how to use textures effectively than trying to "work around" the issue by making more brushes.
Not to mention the fact that a map with only 3 or 4 textures will look extremely boring. Look around you as walk through your day to day routine and tell me how often you just see "3 or 4 textures." I would be willing to bet the only places you would find such things would be in a tunnel/sewer/basement type area. Those places are generally quite boring to look at. =O