You should only use “real” bullets if you want to model them realistically and you anticipate long distance fighting with bullets affected by gravity, wind etc, or perhaps you want Max Payne style slow mo. That way you can have bullet drop over long distances, or have them curve due to wind, or have bullet-time.
If you’re making an arcade style shooter, or your arenas are small, then use line tracing. It’s cheaper from a performance cost, simpler to implement, and you can still do stuff like wall penetration, material hit effects and so on. The end result will be the same from a gameplay perspective which is what matters. Nobody in game will care if the bullets are “real” or not, just that they work properly and consistently as established by the rules of the game.