When choosing a book, I check out it's physical dimensions (width, height, thickness) and its content : number of pages, fontface size and spacing.This allows me to estimate it's "length" and the time I'll take to read it. I also know from experience that I usually prefer longer works, hence my biasing towards them, but depending on the genre and mood, I can choose some outside of my "security zone".
I know I'm far from beeing alone, even if some readers consider on the contrary that a book's length shouldn't be taken into account when choosing a book. For them, it's the intrinsic quality of a work that matters, with proof "The Old man and the Sea", a masterpiece closer to the novella rather than a novel.
Anyways, for a reader, this criteria is difficult to evaluate for electronic books : usual clues (number of pages, format) loose their meaning.
The file size, too dependent to included graphical/multimedia files, is really tricky and allows unscrupulous writers to "cheat".
The number of physical pages can also be "manipulated" by choosing distinct margins, typesets sizes, and line spacing.
A "locations number" (a la Amazon) is also completely proprietary and artificial.
The most "probant" indicator is for me the words number. Easy to compute and check, for "pure" text, it completely conveys a book's length. On the other side, for readers, used to count in "pages", it has no direct "meaning".
So please everyone providing/distributing ebooks (publishers, self-publishers, retailers) please add to the description (meta-)data this number of "equivalent pages" (epages ?). This would be a great plus to customers.
Last note : and don't forget, when you compute this number of epages, to NOT COUNT anything not directly related to the book : TOC, author's biography/bibliography, bonuses, other books excerpts etc.)