No one technique is better than the other. However, the density gradient centrifugation process allows us to obtain cleaner samples, that is, with a reduced percent of sperm with poor motility and other cells.
Choosing the most accurate method depends on the preferences of each fertility clinic, sperm quality, the fertility technique used etc.
Another option is to do a "mix" between the techniques described above. It would consist in using density gradient centrifugation and, with the resulting sample, perform a "swim-up" process. By doing this, we can obtain the best of the best.