The main advantage of obtaining sperm from the epididymis is that they will be motile spermatozoa with a higher state of maturity than those obtained from the testicle, since the epididymis is the place where they accumulate and mature until they are expelled with ejaculation.
In addition, techniques such as PESA or MESA avoid direct intervention in the testicle.
However, obtaining sperm from the epididymis is only possible in cases of obstructive azoospermia (in which sperm production is not affected), so that in other types of azoospermia a testicular biopsy must be performed in search of foci of sperm production.
Similarly, in cases where it is not possible to recover sperm from the epididymis after PESA or MESA, a testicular biopsy can be performed. This would increase the possibility of finding spermatozoa since the testicle is the site where they are produced.