If the car sits a lot, the piston can stick in the caliper no matter which seal is used.  But for light duty and stored inside, the o-ring is still a better bet, due to the piston not being likely to stick in a climate controlled area.

 

But for the street driven recreation car, the original seal takes the advantage.   Which does my car now have?  Original type with stainless sleeved caliper bores, which help prevent corrosion and sticking when not driven a lot.  (Like snow, or sitting in a body shop  )

 

If you can stomp on the pedal a few times every week or so, original. 

If you can't stop the pedal during the down times, o-rings.