I do definitely think its worth the extra money. While hearing the original artist is a plus on the DJ side, the majority of the good bands out there sound JUST like the artist--or even better!
Our 10 piece band took up approximately about the same amount of space as a DJ, wasn't too loud, and DID interact with the crowd--in a REALLY good way. Do you watch Dancing with the Stars or any of those performance related shows? Do you ever see the enthusiastic expressions on the participants faces that just inspires you or makes you say 'Gosh, I wish I could Sing/dance/skate that way?' That's what a good band will do to you and your guests--and the best thing is that there's a dance floor right in front of your guests--they don't need to clear out any furniture from their living rooms to have fun!