If you have an existing website, how does it look? Do your customers find you on different searches? Branding, SEO, and consistent presentation all play an important role.
Another item that is very often at the top of the list is cost; the range for website development goes from zero to many thousands of dollars. Often, the costs grow as the work progresses with unscheduled ad ons.
On the other side of the spectrum; there are companies out there that will design a new site for you for free….but the monthly charges are very high. They make their money using templates and stock photos – over and over and over in websites within the same category. Once they have a base template for the category, they merely drop your company particulars in the appropriate space. It takes very little time to do – thus the price. They make their money on the monthly hosting fees, which tend to be exorbitant.
One factor that matters to many people is it a USA-based company and are you able to understand them?