I'm a regular zone user, and one thing I've found is that certain zones match up better with certain offenses other teams run. Triangles, for example, need a strong forward or center to be effective. Therefore, I'll rarely run a 3-2 against it, as the big would have a fairly easy time posting up if I did. On the flip side, the flex offense emphasizes guards and perimeter play more, and as a result, the 3-2 is often my defense of choice against it.