Have both. Much prefer the Southard. More blade in a generally considered higher end steel. Takes up less space in the pocket. Rides lower as well if that matters. Personal preference regarding shape as well.
Regarding smoothness, I find the Southard smoother. In an attempt to see which has less friction, both knives lubed similarly, both pivots were tightened so I can't feel any side to side play, then marked the same distance from the pivot a point on the spine, and starting at 90 degrees open, see which blade will push the other closed. That's as scientific as I cared to take it and the Southard closed every time first (for both of MY knives).
In regards to side to side play, I feel less flexing with the Southard. If they made a black scaled version of this with the regular blade, I'd buy a second.