Some of us are comfortable with both, some go by a codename all the time, some prefer their real names.

[He and most of the superhero types are comfortable with both. But he's pretty sure that Wash, Chief, and any other people named after states or military ranks are going exclusively by codenames. Meanwhile, there are some civilian types that only used the codenames during battle.]

Usually, we all use the codenames on the field, but outside of missions, usually it's just best to ask what each person prefers.