The Trail YamaLink lowers it about 1.25 inches after you reset sag and are
properly resprung.
The RACE version lowers it half that much, and doesn't have as much leverage
so spring rate isn't as crucial. Most just reset sag and fine tune according
to our simple to follow instructions.
But your rider needs to be properly sprung with or without a YamaLink. With
the 1.25" version many go up for the 10% increase in leverage and for the
RACE version most don't go up unless they're on the border of needing a
heavier spring with the stock setup.
As for which one we can't say. That's why we make two versions because everyone has different needs. Purely subjective. I'd go with the RACE version because hare scramble riders appreciate the extra plushness on the braking bumps and ruts that always hammer them senseless hours into the event.