Is commonly a stout I-beam with one central attachment point on the top and two or more attachment points on the bottom. Because of its design, it must be structurally very sturdy to handle the stresses involved and lifting beams are therefore generally very heavy.
Is a bar with attachment points at both ends. By design it does not do any real lifting itself as it just spreads out the legs of the lifting slings, therefore spreader bars can be made to be lightweight. The top rigging also gives You stability in the lift.
Are multiple point lifting devices with more than two attachment points. They are generally very heavy. Being able to use multiple attachment points may however sometimes be a necessity when lifting complex or delicate objects.