If you go with the cheaper photographer you'll likely be missing out on something you value, performance, talent, professionalism, customer service, timeliness, experience or genuine concern for YOUR wedding.
Find a photographer that you love. The relationship you have with your photographer will show in your photos. Cut corners on something that doesn't last as long as your wedding photos.
Speak with a friend about her wedding, what does she value most about her wedding now? Chances are, it's her photographs because they capture the memory and make it last long beyond your wedding day.