I think Bullets tend to be a little larger and will often have larger IR LEDs. This is certainly true of the Dahua 5442 series cameras that I have. The turret cameras work great, but the IR LED is definitely smaller than the turret version I own. (Although I believe the turret is a variable focal length model and the turret is a fixed focal length model - so maybe that has something to do with it too).
The turrets are definitely smaller in over size. That is a major benefit to that form factor. Turrets aren't "bad" either. I'm 100% satisfied with the results I get with my Dahua 5442 turret cameras.
"Dome" cameras are the ones you generally want to avoid. They are basically turret cameras with a clear plastic dome that covers the lens. These are notoriously bad for reflections affecting the video quality.