Hi,
AFAIK the conditions are checked in the order they appear and stop as soon as possible. In your case in != INVITE it should be the same.
Further, if you use is_method("INVITE") it is even faster.
To be honest, I don't think it really cares in standard scenarios. An optimization of some microseconds is next to nothing compared to the duration it takes to perform a db or radius request for example.
Just my 2 cents, Andreas