There's definitely a difference between worn smooth, and designed smooth. I've used some designed smooth spherical key caps, and they are pretty nice, honestly. Have a totally different feel to them, both because of the texture and the shape. I don't think I would like the smoothness on cylindrical key caps though.
They were always much colder, if that makes any sense. I have no idea why, but they were. Nicely cool, is how I would describe them. But they get slick kinda fast after using them for a while if you develop any sweat or moisture on your hands.