Small business caterer vs. a big catering company
It does not really matter how big the catering company is. What matters - the above mentioned points: level of caterer's responsiveness, detailed and understandable quote and, of course, the caterer's transparency.
Read Yelp and Google reviews, see how their menu looks like and if you are satisfied with the way the caterer communicates with you - go for it whether it is a small family business or a big catering company.