What is the best version of Nosferatu to pick up ? I'd like the most complete version there is.

There are seemingly dozens of versions to choose from, going off:

http://www.dvdcompare.net/comparisons/film.php?fid=857

Their conclusion is

The Kino UE features the longer version, an excellent transfer with 2 score choices (5.1 and 2.0) (the Score was done by the Saarbrucken Radio Symphony Orchestra, see the DVDTalk review for details). Uses Murnau's original names in the intertitles.

The Image SE has a good transfer and 2 score choices (5.0 and 2.0) with an audio commentary and other extras. Uses Murnau's original names in the intertitles.

The BFI edition features the longer cut and a good transfer with more accurate colour tinting than the Image SE. It does have a new musical score by James Bernard (who scored many of the classic Hammer horror movies - including the 1958 Dracula), which has been reported to be superior to all other musical scores for Nosferatu.

DVDBeaver comparison screenshots

I own the KINO Ult. Ed. & am very pleased with it!