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Depending on the size of the company, it might be better to leave subdomains out of it. Subdomains are like brand new sites, so you'd be working a lot harder to get things ranking if you went that route. You don't have a ton of pages per category, so everything might be more manageable under the single domain with good URL structure. Websites that aren't AT&T need all the help they can get, and keeping things in subfolders instead of subdomains will help keep all your authority under a single domain. So, site.com/business, site.com/personal, etc.