When should I use which? Don’t both send info to the client, except datastreams are exploitable but can send more at once, whilst usermessages are safer but can send less at a time?
Datastream is good for the client sending information to the server, or large amounts of information (i.e. massive tables.) It’s a bit easier, and I believe it’s slightly more efficient because it spaces it out over a small amount of time so you don’t crash/super-lag people with excess amounts of networking.
Other than those situations, though, it’s best to use usermessages.
Also, both are equally safe in server-to-client data transfer, since all you are doing is transferring data from the server to the client. However, in client-to-server transfer, you MUST be sure to check the information thoroughly to ensure the client hasn’t tampered with it.