BIA uses a multi frequency method to measure the resistance of the current flowing through tissue, and is one of the highest standards of measuring muscle, fat and fluid in medicine.
DEXA is a dual energy x-ray that measures density of tissue and is the gold standard of Bone Density measurements in medicine.
Both measures of testing have a repeatability standard of 98-99%, only the Evolt 360 is faster, easier to use, and a fraction of the price.