Small businesses are great for dependability and availability. You may be their only account, or one of few, so they'd want to do their best for you. If you have several locations, you could hire one painter per property. After doing a quick Google search I see many highly rated painters in Charlotte, NC.
CertaPro is a chain/franchise type of business, and they have basic quality standards and many employees. I personally prefer hiring small businesses to support the local community over a franchise.