Just my personal experience, but the Tessar on my MXV EV is much better than a later Xenar I had until very recently (sold it at Photographica). Both were very good, but the Tessar had better contrast and was sharper in the only test I ever ran on them. I understand that every single lens is a bit different, and that the history of my cameras may have played a part– neither was new when i bought it but each had been CLA'd in the recent past. Still, the pricelist of new Rolleiflex cameras from one shop in Prov, RI in 1956 showed a $40 difference between Xenar and Tessar lens models. Must have been some difference acknowledged by the company. $40 was not chump change in 1956.