Paul,
Like LaMonte said, you may be incurring an unnecessary expense in replacing the 10 shocks on your coach just because they are 10 years old. Shocks are not a preventive maintenance item, and they should only be replaced if your are trying to repair an issue with a leaking or broken shock or you have a ride or control issue problem that your are addressing.
However, if you are replacing the shocks to repair a problem, your options are either Bilstein or Koni. Bilstein is the original equipment shock that your coach came with, and Koni is an upgrade for a higher control rate at a higher price. So if you are happy with the way your coach rides, but you have one leaking shock, you should replace only that one with a new Bilstein, but if you are trying to repair a ride issue like porpoising, you probably should only replace the 4 front shocks with Koni shocks to gain the added control that the Koni shocks will give you.
Gerald