Having worked in both college and public libraries, it's going to vary very much, based on the size of the library and the specific economic situation. A large academic library system, with lots of subject specialists/bibliographers (think of large state universities, Ivy League schools, etc.) will have more librarians at any given time and, presumably, more turnover over time. Likewise for large public libraries, which may staff branches, have their own subject specialists (think business, genealogy, electronic resources, and so on), etc.
Smaller libraries of either type may be more likely to have only a few professional librarians and less "churn" in their staffing.
Like much of the rest of the job market, the librarian field is a tough one to break into right now. Budgets for the creation of new positions are very tight and librarians who might have been about to retire a few years ago are holding on until their portfolios improve.
That said, it does look right now that academics are doing a bit more hiring than publics. If you visit the ALA JobList board today (12/12), it shows 96 positions requiring masters' or above in academic libraries, while only 30 in publics (this clearly is only a sample of what might actually be out there).
Obviously, though, the wider you can cast your net, the better. If you feel suited to do either type of library, I'd keep looking at both. If you've got geographic flexibility, that helps even more. Keep in mind that, in this job market, part-time positions might give you a good foot in the door (although the benefits part can be tough).
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