[DrEvil]

Any bot with any amount of complexity is going to add more strain to the server cpu, potentially causing lag if the server ends up maxing out the cpu and such. This is especially the case with listen servers, where the computer has to cope not only with the server but with all the different aspects of the client.

That's not to say a 3rd party bot couldn't be more efficient cpu-wise, just that a 3rd party bot wouldnt necessarily let you add as many bots as you like without lagging. It would all depend on the skill of the coder involved and the time they spent implementing the various features efficiently.