Hi there
According to Google, it doesn't really matter - both are separators. I would say whatever keywords / queries you use in the title are substantially more important and where your focus should be. Here's another tidbit from their resource:
"...consider including just your site name at the beginning or end of each page title, separated from the rest of the title with a delimiter such as a hyphen, colon, or pipe..."
I like the look of pipes personally, you'll see Moz uses pipes, and you'll see Google uses dashes. It's really upto you, just make sure your consistent with truthful titles and branding.
That being said, I would watch your duplicate content here and overoptimization for local search. I would focus on local SEO by listing areas you service (like a "Areas we Serve" page or something along those lines) with contact information and finding listings or citations in those general areas (maybe different industry related listings or chamber of commerce, etc). I wouldn't go too crazy with multiple service pages dedicated to multiple service areas because honestly, how much different are services in different areas that are worthy of their own content?
You can also look into service areas by Google My Business. Just be careful with too many local driven pages with same content. Stuff like this can look pretty spammy.
Hope this helps! Good luck!