MKG is a much better rebounder than Green has ever been. He is a better passer. He is also a more efficient shooter from the field and similar from the line. This from a 2nd year player in a bad situation.
I'd trade Green for MKG straight up and wouldn't give it a second thought. Of course that trade doesn't work financially. Maybe something like Humphries and Green for MKG and Gordon. Perhaps send Lee and also get Biyombo or send Bass and get Biyombo and Haywood.
Green has much more value than MKG at this stage of their careers. MKG's shooting is a big question mark and that's his let down.
Greens defensive capabilities make up 50% of his value and his three point shooting is becoming more and more deadly.
The straight swap never happens because from Danny's perspective you've got a very reasonable contract at 9 million a year on a guy who'll get you 16 points and defend the best small forwards in the NBA at an elite level.
If we want to contend he's a great 3rd option scorer next to someone like Melo and Rondo. Again, his defense and versatility is just phenomenal value for a team that wants the ultimate role player with the occasional All star level game.
Any Green for MKG deal brings back immediate expirings and/or picks
ie:
Green+Brooks+2nd rounder
for
MKG + Ben Gordon (Danny squeezes very hard for future lottery protected pick.)