BIG difference. A properly rifled pistol will hold less than a 1" group off a rest at 25 yards - more accurate than ANY modern 'sporting' pistol. If built with a section of rifled barrel, it can be just as accurate, but will require a LOT of powder & a tighter combination to do it.
A smooth bore pistol is no where near as accurate, in fact, you'd be hard pressed, I'd expect, to shoot a 4" group at the same range, whereas a reasonably long barreled gun with smooth bore can actually shoot a 1" to 1 1/2" group a 25 yards.
Smoothbored pistols are usually without a rear sight, but not always. A rear sight would certainly help, accuracy wise.
Green Mountain makes finely accurate pistol barrels. Track sells them.