I do live performance videos and use both a t2i and a VIXIA. While you indicate that manual focus is important you need to be aware that focusing on moving subjects during shooting is really difficult using the small LCD screens of either of these cameras. The VIXIA does a great job of keeping auto focus on moving subjects. If you do decide to go for the t3i I strongly recommend that you look into the free Magic Lantern firmware package. Its focus aids are a tremendous help.
I use dual system sound with a Zoom H4n recorder and sync in the edit but that adds cost and work. Sound is really a whole different set of issues but it is critical in making good videos.
