An obvious start is looking at the genres. Leaving the largest, romance and crime/thriller, for another time I'll start with the fiction genres with the least amount of books. Harlequin published one sports novel and five war novels. CPF none. Harlequin published seven science fiction books, CPF one. And finally CPF published 11 classic novels (authors such as Balzac, Stendhal and Tolstoy) and two juvenile books, Harlequin none from either group. Nothing much to be learned here except that many types of stories were equally unpopular in French and English Canada for a general paperback publisher's audience.
The one genre with a difference is westerns, Harlequin published 75 (16% of their total). Fifty-one were published in just four years (1950-1953). During these four years CPF published 56% of their books, including a lone western. Why the dramatic difference? I don't know. Were westerns simply not popular in Quebec at a time when their popularity peaked in English Canada. Or were there other Quebec publishers that met any demand for westerns.
The CPF western is Les Bandits de l'Arizona by Gustave Aimard (French, 1818-1883). Below is another paperback edition from 1953. Information about CPF is courtesy of Literature en poche: Collection "Petit Format", 1944-1958: repertoire bibliographique, Richard Saint-Germain (Sherbrooke: Les Editions ex Libris, 1992).
Here are some Harlequin novels from genres discussed in this post.
Harlequin 6 - 1949
Harlequin 78 - 1950
Harlequin 238 - 1953