The RM model of Officer training suits them. It probably wouldn't suit the Army, which is a much bigger organisation. It is also worth remembering that the RM YO's course is the CC and PCD combined, so to ascribe its whole length to purely officer training would be a false analogy.
This is very much a general rule, not a description of 100% of RM officers and two of the very best commanders I've ever worked for have been RM. That said, they were the exception of those RM officers I've met. I wonder if the less academic nature of the training (they only do 1wk at Faraday hall) and the increased focus on junior leadership isn't a hindrance once you've moved past your first troop command role.