My mother tongue is French so I would prefer one in this language but I'm also interested in English ones, especially if they can be considered of much higher quality/completness.
I've heard of the Greek-French & French-Greek dictionaries written by Δημήτρης Παντελοδήμος. The first editions (1995) were published with the Kauffmann edition and the latest with the Τσιγαρίδα edition.
The 2002 Greek-French edition boasts 150,000 words while the newer mentions 140,000... so I wonder if the latest edition is the best and what happened to the 10 thousand words...