The XA10 has the most features of all the camcorders in that series. But all in the series, M400, M40, M41, G10 and XA10 are capable of giving the same quality picture.
I would start with your budget first then cover as many of your needs as possible.
The wedding I shot this summer turned out much better than I expected but I sure wished I had two camcorders. That would have prevented me from missing the Ring Barrer drop kick the pillow. Imagine my frustration as people are coming up to me asking "did you get that?" But my camcorder was on the tripod in place for the march and vows. The action was blocked by a decoration. Also, a second camcorder would have made editing easier.
Sound is very important but by all means don't get carried away. Most audio tracks can be cleaned up in post. I use audacity, it's free. It's hard to fix extremely low audio. A $20 mic in the right place is better than a $400 mic not.
If you're going to shot weddings for hire, redundancy will be your friend. I guarantee you will be more critical of your work than your customers. When you find yourself rendering to DVD for most customers, you'll realize your equipment is overkill.
Good luck. A new venture is always exciting and the great thing is that money can make it all better.