Use Quality levels 4 and 5 sparingly as they are the most costly. Save them for jobs that require the highest precision and smoothest finish possible.
Quality level 3 produces a smooth edge at a moderate speed and is used for most machining.
To optimize cost and precision, use different qualities for various part features. For instance, use quality 2 for the outer perimeter of a bolt flange to reduce cost, and use quality 3 or 4 for the inner diameter for a precise fit.