Allegro:
Very soft, slightly thinner material but not too thin. Ruffles at the knees. Slightly longer than knee length. Cut very beneficial. A little less "hold".
Killer Caboose:
Slightly shorter (ends right below the knee), thicker material (not much thicker) with a little more maintenance / something formative, but also more rigid (but only in comparison, does not in itself seen). The cut on the butt is elaborate and looks m. E. better than in the Allegro, but also more to the sport pants. To counter this impression again, the Killer Caboose has little playful ruffles at the knees, you may need.
I would decide on the basis of the higher comfort for the Allegro.
