TCP is quite fast, I'm always amazed how fast we can deliver a single line text message over the internet these days.

I used TCP for my chessgame, however the data that had to be send over the socket was very tiny compared with other games, so that's not an honest comparison! I think TCP is fast enough to be used over a LAN, a lot of games seem to do it, although a lot of games seem to be using the IPX protocol too, dunno why. UDP is a nice and fast protocol, but you'll have to do some sort of CRC checking yourself to ensure that the package arrived the same way as it left the senders socket!

A plus of TCP packages is that they arrive in the same order (well they are placed in the correct order by a lower layer than the software layer I believe), however with UDP the packages can arrive in a random order and they aren't placed in the correct order by any network layer, so you'll have to solve that too and if a datagram is lost you'll have to re-request it too, but even then it's faster then TCP, due to the size of the datagram, only a lot more work to implement!

But knowing you, you knew at least half of this stuff allready!