I have Pinski's book, but not the ones by Obodchuk or Lakdawala, so it's hard to compare them.
From the sample pages [1][2] it looks like Obodchuk doesn't cover Glek at all and Lakdawala has about 30 pages on Glek. Given that Lakdawala's book is not a repertoire book, but a move-by-move, he probably goes deeper into describing individual moves. With 5-6 pages a game he likely covers about 5-6 games in total.
Pinski has about 50 pages on Glek, deals with 4...Bc5 (10 games), 4...d5 (13 games) and some sidelines (7 games; Be7, g6, Bb4 and Nd4. Note: doesn't deal with 4...Nxe4).
If you're looking for a repertoire book, I would go with Pinski.
[1] Obodchuk: https://www.newinchess.com/Shop/Images/Pdfs/959.pdf
[2] Lakdawala: http://www.everymanchess.com/extract/Four%20Knights%20MBM%20extracts.pdf

I am starting to play the Four Knights Opening, and am thinking of getting a book on it. My main interest is the Glek Variation (4.g3), though I have also tried the Scotch Four Knights, and would be interested in looking at the Spanish, too. I am hesitating between the books by Pinski and Lakdawala (the one by Obodchuk apparently concentrates on the Spanish). Any recommendations, please?