Unlike sleeping bags, beds have a shorter cooldown timer. You only need to wait two minutes to use a bed again after dying.
However, using a sleeping bag in the same cooldown radius as your bed will trigger the cooldown for both items.
Beds must also be placed on a foundation surface to operate.
The shorter cooldown timer makes a significant difference, particularly in PvP situations. If your base is getting raided, those extra three minutes are invaluable.