Later engravings of Jurgenson and Édition Russe de Musique scores in Germany often contain revisions to the original, generally in the form of additional markings, whereas those republished by Soviet State Music Publishers prior to 1959 usually do not.
The most authoritative complete edition is the Medtner Collected Edition published in 12 volumes by Moscow State Music Publishers in 1959-1963, hereafter referred to as the 1959 Collected Edition. Edited by Sofronitsky and Goldenweiser with the aid of original manuscripts provided by Anna Medtner, it corrects errors in earlier editions and incorporates many changes made by the composer during his lifetime. Copies are scarce in the west, but the Bodleian Library (UK) and Yale University (US) each have a complete set. Westminster Music Library has volumes 1, 4, 5, 7 and 11 available on loan. I have them all except volume 6; if you know where I might obtain the missing volume please let me know! The Dover edition of the Piano Sonatas and Fairy Tales is based on the Collected Edition apart from (strangely) the Op 30 sonata.
Moscow "Muzyka" republished all Medtner works from the Collected Edition in later years, often more than once, and re-engraved some of them. They currently offer Opp 38, 39 and 41 which can be obtained from Ruslania. Many earlier Muzyka publications are downloadable from IMSLP or other sites.
Christoph Flamm has produced critical editions of Op 39, Op 49 and Op 51 for Zimmermann, and Zen-On has published a critical edition of Op 38. A few other editions have appeared in countries where copyright has lapsed; those seen by the author have reproduced previous editions.