Put a 170 Jr. GS race ski next to a 170 GS cheater ski and flex them - you will be surprised if you think the Jrs are soft. We have had numerous pairs of Jr GS race skis and they have a flex pattern that is quite stiff. The "Junior" term applies to size of the ski.
The GS cheater skis are the way to go because they are easier to ski - they have a wider tip and tail, more sidecut.
The Jr race skis conform to FIS regs for Children 2 (13-14) or Children 1 (11-12). Those regs were dropped and for 2011-2012 there are no rules for 14 & under except for stack height and boot height. At age 15 they have to use a GS ski with a 21 meter turn radius for USSA, and in FIS 23 for girls, 27 for boys.
Now that there are no rules for Jr race skis I would expect them to go with the easier skiing dimensions of the cheaters. However, there is uncertainty out there with what the FIS will do with GS regs and what the USSA will require for youth.