RTS Multiplayer Synchronization Check

I have been working on a lockstep implementation for an RTS game (see http://www.gamasutra.com/view/feature/3094/1500_archers_on_a_288_network_.php if you're not familiar). I have completed the basics but what was wondering the best way to check that all clients have the same game state. I see two ways of doing this (feel free to point out another way).

I can either create a hash number of the game state. I assume this would involve calculating a hash of every unit position rotation and state. And then check the hash against every other client to very synchronization. This sounds like it would be a lot of work with many units in the game though so I'm not sure how feasible that option is.

The other way I could do it, is not check the game state at all and out of sync only occurs if a command that has been issued cannot be executed on a client. However, this wouldn't detect them straight away.

I was just wondering the best way to do this. Cheers.