While both are pretty appalling, I'm going to have to go against the general consensus and say that while I don't necessarily find the Smiler rougher than Saw, I certainly find it infinitely more uncomfortable and less enjoyable to ride.
As far as mechanical smoothness on the majority of the Smiler's trains is concerned, there admittedly isn't a huge amount of rattling or that odd 'shuffling' motion experienced on Saw (presumably as a result of the change in weight distribution over the wheel bogies brought with the new train design. This is something I'm keen to monitor over the coming months/years). However, the nature of the layout and the radical, tight profiling that Werner had to use to bring it to life render the physical ride quality atrocious. That's even without regarding the inexcusable and horridly violent jolts on both the first inverted drop and the exit of the cobra roll.
While I'm the first to admit that Saw has some serious roughness issues, its drawn out layout and shallow, subtle transitions allow for a ride with just enough time and space to properly brace for each element - Something that is practically impossible on its younger sister (which is more a case of clenching your entire body throughout the ride and incessantly praying for for it to end).
Generally, people must remember that it's not always mechanical faults that make for a violent coaster. Botched/poor transitions and bad profiling/heartlining are almost always to blame for severe headbanging. Max Adventures Master Thai proves that better than any other coaster I've ever encountered.
Please, feel free to ignore me. I'm just jaded.