Prices may differ dramatically, but probably not. Caterers are a competitive business and all price out their services somewhat the same. Your choice should consider style. Make sure your caterer is someone you feel comfortable with and trust. You need to share their taste and style.
Food preparation is much easier in a familiar location.
Try to find a caterer who doesn't include gratuities in the per person price. This allows you to tip as you feel appropriate. Are the entertainers, photographers, etc. Assign a friend to let you know when you're a half hour to closing, before overtime charges start to accrue. Professionals who have worked together before will be more familiar with one another's quirks.