This is a bit of a noobish question but...

I've been solo mining various coins over the last couple months successfully on one machine.  I recently set up a second machine and have it mining away without issue as well.

My question is regarding efficiency.  If I'm solo mining on two machines on a LAN, with one machine running the coin client in server mode and mining, and the other machine's miner pointed at the client on the first machine...is this sufficient?   Does the client somehow share out the work between the two machines so they are not "working against each other" (say, working on the same block)?  Or is it better to use p2pool with multiple machines?  

Thanks in advance!