The disc jockey needs to adapt to any circumstance and adjust quickly. It is a safe bet that a company or individual that performs full time can devote more attention to your event. Keep in mind that you are their only livelihood. With a part-time disc jockey they have another source of income and may not need your business. The professionals will always work to get your business.
Professional corporations offer many advantages over the part timer.
Usually they are insured, meaning that they are responsible and covered if an accident occurs while at your event. More and more banquet facilities are requiring certificates of insurance from their vendors and suppliers. It is not unforeseeable that in the future a hall may refuse entrance to a company that does not hold liability insurance. A professional has a plan in place in the event of a major equipment failure. Ask if your prospective disc jockey carries back-up equipment to every event.