I am only just starting to think about this stuff myself, but I guess a camerapick results in an instant hit whereas a moving bullet will take a finite time to hit. Not much difference at close ranges, but can make a difference at long ranges especialy with slower moving projectiles.
Reducing the amount of polys is always good to keep your FPS high, but you could make a bullet using a sprite or single quad (2 tris) or maybe using a single surface system. Depending on how many you need to draw, its unlikely to be a major contibuter to total polys? I guess their would be another slight performance hit due to actualy moving the bullets. I dont know, but I guess the collision tests might be your biggest performance hit?
Reducing the amount of polys is always good to keep your FPS high, but you could make a bullet using a sprite or single quad (2 tris) or maybe using a single surface system. Depending on how many you need to draw, its unlikely to be a major contibuter to total polys? I guess their would be another slight performance hit due to actualy moving the bullets. I dont know, but I guess the collision tests might be your biggest performance hit?