Until a not too long ago it was a tie between the Tribord Easybreath (check out the review here) and the Seaview 180 (old version, review here). With the introduction of the V2 of the Seaview 180, we do believe that we found a new ruler. You can check out our picks for the best full-face snorkeling masks here: https://www.deepbluediving.org/best-full-face-snorkel-masks/