Rank sites locally to generate leads

I`m starting to rank sites locally to generate leads and I`ve got the ranking aspect down, as I do local SEO for my 9-5. However, I was curious on whether you guys would structure the site as city.domain.com or domain.com/city. I`m leaning toward domain.com/city as it`s much less work. However would a subdomain be more optimal due to Google viewing these as "seperate sites" to some degree?