In my opinion Chris Higgins is Montreal's top forward. He comes with no baggage and is a sure bet to play in the NHL atleast as a 4th line forward. Kostitsyn and Perezhogin are highly skilled, but I think that raw offensive ability factors out the high bust-potential with players like Andrei and Alexander. Higgins is a guy that may not score, but he'll contribute in other aspects of the game, the other two would have a tough time helping a NHL club if they're not scoring.
Anyways... as for Wellwood vs. Higgins, I'm a huge fan of Chris Higgins and a fan of Wellwood, personally I think he's extremely overlooked and underrated by fans, even Leaf fans including myself. His skill level in my opinion is on par with many notable prospects around the league, the question mark is his skating and average defensive game. His skating isn't bad, it's just not eye-popping, not what you'd expect from a small forward that tore up the OHL. He has very deceptive speed and as long as his strength improves, he has a very good chance at making the NHL. Having said that, I think most Leaf fans don't have high hopes for him like they do with Steen, Colaiacovo, etc... I think he'll be a guy that'll make it to the NHL and surprise many.
If it were up to me, I'd take Higgins over Wellwood because of the security, if I had the luxury of having a lot of depth in the system up front, I would take Wellwood because I think his ceiling is higher, his skill level is higher, and if he develops into a NHL player, he'll produce more offensively.