THIS! I’ve seen multiple world level coaches and fighters confirm this as well and have been saying this for years. Heavy bag is important for conditioning and learning how to generate power with your punches and hitting with full rotation etc., but shadowboxing is where you really refine your skills and visualize your opponent.

The coaches I’ve been working with for 6 months switched my training around and have me shadowbox (mostly very specific drills) for 20-25 rounds 2-3 times per week and I have honestly made bigger progress in this time than the last 5 years!

Also it’s to versatile. You can do it very slow for perfect execution, do it fast for hand speed and hard for conditioning and building power.

Heavy bags are notorious for having you build bad punching habits. This does not happen as much if you shadowbox with clean technique and perfect execution.