The music you choose for your reception can have a large bearing on the success of the occasion. While you're planning your nuptials, at some point you're going to have to decide whether you want a band or a DJ to perform. Your decision should be based on what you want out of the musical offerings.
For instance, if you'd rather have everyone singing along and dancing to familiar tunes after a few drinks, a DJ is probably more up your alley. However, there's something to be said about the spontaneity of a band that simply can't be replicated by one guy standing in front of a turntable deck.
Of course, DJs are going to be less expensive almost across the board, assuming you're not looking to get Fatboy Slim to spin at your reception. You should also take space into account when making the decision. If you've got a small space to work with, a band may simply take up too much to be worthwhile.