If it comes down to having a band or the Cathedral, i'd go with the Cathedral. When you have a band performing, it always feels like you have to listen to them, or at least clap at the end of every song which later on in the night gets tedious.
Looking at your age, chances are you've got a few mates like me who are into proper clubbing and like good nights out (maybe you're one yourself) and in this case, at about 10/11pm, they're going to want to dance around like lunatics to the songs they like, and not what a band is playing (dependant on what the band plays of course).
What my mate did for his wedding was ask everyone who he invited for a song recomendation to add to the song list he gave the DJ so that at least for part of the night, people were getting the music they liked, as a good DJ should have a good selection of music that complements other songs so that a slow song isn't randomly put in the middle of a r'n'b heavy set.
TL;DR version.
Cathedral > Band. Your choice of music with the DJ in the venue you want, or music which won't be all your choice in a venue which may not have been your first choice.
Obviously, some will disagree with all of that, but that's my view.