A coverage of 30X means that each individual base will be checked 30 TIMES to guarantee the sequence accuracy. The disadvantage is that it is a bit more expensive. The advantage is that gathering more information result in higher accuracy and complete analysis of your health predispositions. We do recommend this analysis when the individual is aware of some adverse conditions in the family. To have the full text of your genome is a lifetime investment that can help you live longer and healthier.