They are all important. If you aren't doing them all, you're wrong.
That being said, shadowboxing is hands down the least utilized and most overlooked of the 3. Someone mentioned they don't know anyone that shadow boxes for multiple rounds. Well you should be shadowboxing multiple rounds, several times a week.
If you are only shadowboxing for 20 seconds after wrapping your hands, then you are selling yourself seriously short.
That being said, shadowboxing is hands down the least utilized and most overlooked of the 3. Someone mentioned they don't know anyone that shadow boxes for multiple rounds. Well you should be shadowboxing multiple rounds, several times a week.
If you are only shadowboxing for 20 seconds after wrapping your hands, then you are selling yourself seriously short.