Why for Dallas:
Dallas has openly stated that they want to obtain a point guard if they are to make a deal before the deadline. Brandon Jennings is a very good point guard who could flourish running the pick and pop with Dirk. During their 2011 title run Dallas lived off of a pick and pop with a combination of Dirk Nowitzki and Jason Terry/JJ Barea/Jason Kidd, all of which were adept long range shooters. Jennings would bring another long range shooter in the fold, so that Dallas could get back to its bread and butter offense.
Why for Milwaukee:
The Bucks would have trouble parting with Brandon Jennings, but this return would make his leaving more palpable. In moving Jennings for Collison they would be getting the pass first point guard that could make Monta Ellis play up to his potential again.
Shawn Marion would bring the Bucks a veteran with playoff experience. He also would give them a solid starter at what has been their weakest position all season, small forward. His defensive prowess combined with Larry Sanders and Luc Richard Mbah a Moute would vault the Bucks into an upper echelon defensive team. Milwaukee is also not a very good defensive rebounding team, bringing Marion into the fold would certainly help rectify that problem.
On top of getting Collison and Marion, the Bucks would be ecstatic to get out from under the awful contract of Drew Gooden. Moving Gooden would not only help their cap situation but it would also free up more time for John Henson and Samuel Dalembert to play.
Check out the other posts in our February Trade Rumors Series: