the cannon is worth less because it has capture conditions that the rook doesn't have. Of course, it is much better than a chariot in some cases! I would say a soldier having crossed the river is worth more than an advisor or elephant because it isn't constrained into path movement.
Also, NO WAY a horse is worth the same as a cannon. You can take a horse with a cannon straight off from the starting position, but it is a very bad move to do so.
(hide) If you want to find out more about some games you can check the links section and see if you find any interesting links there. (pauloaguia) (show all tips)