I would strongly suggest upgrading both machines to Snow Leopard.

Leopard is better than Tiger for performance using Catalyst.

Snow Leopard is better than Leopard for performance using Catalyst.

If it's your Cat MacPro then clean install. This is the easiest way to make sure you don't encounter problems.

Honestly though, it doesn't matter which version of OS X you use on either machine. If you are using Apple Remote Desktop, it will work across both machines independent of platform.