@Sebgo We moved my son from the TRA at age 10 when he was getting into 28 mph 15 off to the Vapor. He started with a Vapor graphite and when he was 11 moved to a Vapor Pro (not out of necessity, just the opportunity to get a new ski became available). He stayed on the 63.5" Vapor through last year when he was 13 (~115-120 pounds) and getting into 28 and 32 off at 34 mph. He is now on a 65 Vapor pro.
Many of the kids I see at Nationals are on the D3 kids ski, Goode or Radar. It is unlikely the ski itself will make a big difference in their skiing but at a level around where your son is now it should help him progress quicker.