I don't hear anyone saying smoothies are obsolete, but they are definitely not as accurate as a rifled barrel with sabots. The experience of the shooter obviously comes into play here.
The biggest advantage of the sabot, at least IMO, exist in the 20 ga. A 20g sabot now has enough down range energy to drop deer out to 150yards, and with less recoil than a 12. This to me is the only reason I bought the rifled slug gun.
That thread you referenced doesn't mean anything to me. You can give 5 people the most accurate rifle in the world shooting from the most expensive and fancy rests and each one of them will have different results. To tell you the truth, I would be much more impressed to see someone drop a deer in its tracks at 200-250 yards with a centerfire rifle shooting from a free standing position than any bench shooter shooting 5 shots in one hole at 100 yards.