Well, both are done "through the client" - one uses the scripting engine, one is done by text substitution in the "send" box.
I suppose that @variable might be slightly faster if you weren't doing scripting for any other purpose. If you are already sending to script then it is using the script engine anyway. Also, if you check "expand variables" that is an extra step the client has to do (to look for @variable) which it doesn't otherwise do.
As I said, the difference would be negligible. You may as well worry whether long or short variable names would be faster. I would use whatever is easiest under the circumstances, and which is easiest to read and maintain.
The GetVariable and SetVariable functions would be through the client... is that the same as using @Variable to get a variable? How does this compare with getting and setting the variables through the script?
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