they are a more accurate version. Paveway is the "kit" that turns a "dumb bomb" into a smart bomb. They use GPS/Laser designation for targeting.
So they arent as large as the FAB 1500 ( 3000lb ) - Paveway are usually 500lb - but what they give up in explosiveness, they make up for in accuracy. Especially laser guided. You can have a spotter on ground "lighting up" target ( window on a bldg ) with laser, well out of range and put that bomb thru the window.
The other aspect- they also make a "bunker buster" Paveway that can penetrate up to 60 ft or thru up to 6ft of concrete.
But the Paveway 4 is the most recent iteration - so technologically way more advanced. ( also comes with the ability to defend against EW )