All the seatposts listed here a for the standard "two rail" seats. Given that, the two main systems for attaching the post to the seat are called "one bolt" and "two bolt". The "one bolt system has a rocker clamp" which you adjust and then tighten the bolt. The two bolt system has no "rocker". Instead you adjust the angle depending on how much you tighten the front or rear bolt. The two bolt system is easier to get exactly the seat angle you want.
The old "one bolt" system had a toothed rocker, and a single bolt. You adjusted the angle of the seat with the rocker and then tightened the bolt. But tightening the single bolt would often change the way you wanted the seat, and you would have to try again.
A better system is the two bolt system whereby you balance the tightening of the front and rear bolt to get exactly the angle you want.
See Bikebarn video