Yes they work better because cooling pads do not always blow at the right part at the bottom of laptop where air intake is and at best hit that intake with just a small part of air they move. The plastic bottom of laptop may seem cooler but not inside where it matters.
Vacuum ones don't care where air is coming from so full effect is possible. In any case, bottom should be left open to air intake and holding it on a soft surface can impeach air intake. If you must use it in bed or a place like that, even on your lap, I'd suggest you get some stand for it even without fans.
Bottom (excuse the pun) line is that bottom intakes have to be clear all the time or nothing will help.