Oooh... I didn't hear about this show. I saw Muse play at the State Theatre in Minneapolis in 2006 when I was living there (I mean RIGHT there, I just had to take an elevator down from my apartment and go down the hall to get there). I really loved the show. They had a lot of cool props on stage with them, cool lights/videos and they sounded amazing live.
I would go to the show. You can go to the masquerade next year. Also consider that if you do go to the masquerade are you going to be thinking, "I could be seeing Muse..." all night? You might not have as much fun if that were the case.