Just to spell it out for anybody else who might read this thread;
Fully clipped; all track windows are cut and all cross-members have metal clips attached.
Clipped every third: Track windows are cut out in a cut-cut-uncut-cut-cut-uncut... pattern. Every third cross-member is clipped (between the two cut windows).
Pace 3: Track windows are all cut out, every third cross-member is clipped.
The best option for durability, speed, and slider life is fully clipped.
Some years ago, the track manufacturers (camoplast in particular) realized that they could save a pile of money by reducing the number of clips installed on the track. They marketed this option as an enhancement, stating that it would hold more snow in the track. It turns out that what holds snow in also prevents snow from GETTING in, and that having fewer clips means that the clips that ARE present are rubbing much more forcefully against the sliders, thus causing them to wear out more quickly. Pace3 is like a clipped-every-third option that is compatible with external drive sprockets.