The only chance of the new J will be on the 763. If you take a 333 there is a very small chance that it is subbed to a 763 or 343, and you could end up losing your seat. But the chances are likely so small that I wouldn't worry too much about it. The 333 is the nicest in terms of entertainment, the 763 could be good as you may get a single seat if it's old J, or you can get lucky and get new J.