I think with the multi cat, Glass is the favorite here (long term) here but it's close and I think Kotkaniemi should also give you some peripherals.
Also to consider is Kotkaniemi had a pretty darn good rookie season and is going to have a much easier time being a top 6, if not top line guy in Montreal than Glass will in Vegas. Who knows if Glass makes it; you can never know until you see them in the NHL, no matter how highly touted.
If you are stacked and just looking for boom or bust potential, then Glass, but I go with Kotkaniemi here.