In general, larger searchcoils will give better depth with larger targets and better ground coverage. However, sensitivity to smaller objects may be sacrificed. Smaller searchcoils will offer greater sensitivity to smaller objects and improved target separation in trashy soil.
A third style, the Printed Spiral, is made only by Tesoro for use with pulse induction circuitry. It offers good sensitivity to a broader range of target sizes and improved sensitivity to less conductive targets such as fine gold chains.