I can tell you the only real difference between the two HDPE shooters is the lack of two finger grooves and a 5 degree or so angle difference in the cant of the handle... A child would be more likely to enjoy the Cubscout, whereas the Standard Sideshooter is sized and shaped more for an adult.
Here is an older posting but one member shows a pic of a BoyScout beside a SideShooter. The differences that I see are HDPE vs PolyCarb and different fork tips. The PolyCarb BoyScout has universal tips and the HDPE SideShooter is TTF only. I only have the BoyScout.