If you are leaning towards having a band play at your wedding reception, then it may be in your interest to know that bands are generally considered more sophisticated and are better at pumping up the crowd compared to a DJ. Bands are also good at working with the theme and tone of your wedding based on the instruments they play and the way they play them. If you get a good bandleader, they can also perform the master of ceremonies during the reception if you want, interact with the guests as they dance and notice the feel of the room so they can choose songs appropriately. A good wedding band will also play continuously, taking 5 minute breaks during lulls.
The pros of a wedding band are fairly obvious. When you have a live performance, the experience tends to be more pleasurable and exciting. Since the songs are played a little differently, anything can happen to raise the excitement at the reception from a stirring solo to an amazing trumpet solo that picks everyone off their feet.
One of the pitfalls of bands is that they tend to be more expensive than most DJs. Also, if you hire a lounge and instead of a true wedding, than you need to make sure they will perform for the period of time you expect. Since lounge bands generally take a 20 minute break every hour, then they may not work for your party because you may more continuous music.