I don't think it's one or the other. If you can earn top 6 minutes and play with future hall of famers and experience the pace of the NHL then there is nowhere better imo to develop.
So I am mostly interested in developing the players, winning a few more games is just icing on the cake.
The problem with calling up young players, who project to be top 6 players, to an NHL team is burying them in bottom six roles and giving them no pp time. But when you can afford to give them major minutes then it's a great place to develop imo. This team can afford to play a guy like Kaliyev next to Kopitar all season long, his weakness is his defensive play right? So where will he learn to play better Defense, next to Kopitar on an NHL team that will demand it, or back in the CHL where he can get away with whatever he wants? That's just one example.