Harry,

_Shanties from the Seven Seas_, unabridged (1961), is the most inclusive and contains the most items. (I will not say "comprehensive.") Don't expect it to tell you all you'd want to know about the chanty genre, or to give you all the items with historical accuracy (I'm sure you don't), but as for Hugill's works, this is the one that fits your request.

That being said, what is in the unabridged edition that is not in the much more easily found/purchased abridged version? Well, the vast majority of extra consists of songs in languages other than English: Norwegian. Swedish, Plattdietsch, Hochdeutsch, French, Welsh... And most of that is not some original "collection" of songs by Hugill, but rather he has compiled those texts from books published in Norway, Germany, etc. So, one can get some French songs from a French-published book on "Chants du Marin" or have them filtered through Hugill.

Other extras in the unabridged are reproductions of songs that are, again, not anything original, such as a Stephen Foster song that is the inspiration for a chanty or something like that. Again, not really useful. I'd say unless you are just a completist who wants to have the full Hugill for the sake of it, just get yourself the abridged edition published by Mystic Seaport.

Hugill's subsequent books:

- The Bosun's Locker, Collected Articles 1962-1973 (Heron Publishing, 2006)
This is a continuation of the soft-scholarship in Hugill's _Shanties from the Seven Seas_, bits and pieces of further thoughts and repertoire items that didn't get into the 1961 work.

-Sailortown (1967)
Not about chanties.

-Shanties and Sailor Songs (1969)
This is as if Hugill decided he needed a more concise book, after the sprawling and badly organized _SfSS_. Hugill's tone of presentation is much more positive, like "This is what it is" as opposed to the SfSS research tone, "This may be what it is" :) In other words, things are boiled down and put in a positive fashion for readers who don't have time to deal with uncertainties and would rather have things told to them as if they were cut and dried. The repertoire included is selective. If I remember correctly, there is no NEW repertoire that wasn't in SfSS. Also, notably, the subject goes beyond chanties to "sailor songs."

- Songs of the Sea (1977)
This is more of a popular "coffee table" book. The music notations and lyrics are impossible for me to read due to the color of ink and the cursive writing. It is geared towards Hugill's international audience, that is, making special appeal to non-English-speaking Europeans, with a lot of Dutch, German, Swedish, etc songs.

I have a series of YouTube playlists in which I have rendered -- a fancy way of saying I have turned all the ink on the printed page into singing -- all of the items in Hugill's unabridged _SfSS_. The relevant purpose of doing it was just that: to somehow make what is on the printed page audible (even if that means having to fill in gaps or guess at corrections). Make other judgements about my "performances" and their intent at your own peril. It was made over the course of several years with a lot of development/change in style and approach. Anyway, it's a reference point (page numbers linked to Hugill are given) to what you're seeing in the full Hugill.
https://www.youtube.com/watch?v=RVmCbsMzHrE&list=PL58B55DD66F22060C&index=1

Among the popular sources -- compilations meant for practical use -- of chanties, I can also recommend:

Whall - _Ship, Sea Songs, and Shanties_ fourth edition (1920). The tunes and lyrics are accurate. Ignore what he says about the material though.

Bullen and Arnold - _Songs of Sea Labour_ (1914). A very good reflection of the repertoire of a 1870s chantyman. However, some of the tunes are notated poorly. Also, beware that they present the chanties honestly, as lacking any fixed text, which means you have to supply your own lyrics -- which you should.

Doerflinger 1951/1990. Meticulous and accurate, though not as geared towards practical use due to the descriptive presentation of individuals' renditions (i.e. as opposed to prescriptive). This and works like Sharp (English Folk-Chanteys, 1914) are convenient sources of actually-sung lyrics.

My advice... as weird as it will sound... is to read Hugill for the contextual background... then reference Bullen and Arnold for a real picture of the actual repertoire of chantymen... then secure the tunes from Whall... and finally flesh out lyrics with ideas from Doerflinger and Sharp.