The performance difference between spawned and 'placed' AI could be much greater, as the server performance with the example mission that spawns AI may reach a minimum level with fewer AI.
For both missions, there are 40 groups of 5 basic infantry used on both sides, with a simple move waypoint given to each group leading to the opposite side of the runway (where the opposing side starts).
The code for spawning the AI is executed in the init.sqf.