Lehkonen has more value than Pulju in my opinion. Pulju has done nothing in the NHL. Lehkonen has proven to be a valuable, young top-9 winger who drives the net and can be a trigger man. Obviously he's not scoring this year so the frustration might be setting in for MB/CJ. Lehks for Pulju would be interesting though.
I would do Lehkonen for Puljujarvi.
Lehkonen is at worst a 3rd liner and at best a 2nd liner.
Puljujarvi at worst is a non-nhler and at best could be a star in the league. I would take the risk.
Not sure if bergevin would though since Lehkonen has character, is hard working and is good defensively.
Also Pulju will require waivers next year, so you have to be confident he can be an nhler next year.
Not happening, but something around Hudon+ for pulju would be great for us