It should always be one website per business. Not only for SEO reasons but for usability. Just have one and show the 4 locations on the contact page. No sense in duplicating the services or the about page for each website.

The SEO advantages are that you have on bigger site on (hopefully) page 1 of the rankings than 4 on page 50 of the rankings.

Maintaining the local feel can be done through your content and imagery, not the URL.