The bear: Zafar Khan, Société Générale

Boeing’s (BA) commercial business is enjoying a long backlog of orders, as airlines continue to order fuel-efficient aircraft. But Boeing’s suppliers need to quickly increase their output — and they may not be able to. Boeing also delayed reporting the cost of development for the Dreamliner until it started producing the plane. So margins will be small as they spread the expense across the first 1,100 Dreamliners they make. Finally, the U.S. is entering a long period of gradual defense cuts. Boeing is valued like other large civil aerospace stocks, yet 40% of its business comes from defense. Civil aerospace companies trade at 12.5 times 2012 earnings on average. The defense guys trade at 9. Factoring in both sides of its business, Boeing should be at 10.5, but it trades closer to 13.

The bull: Noah Poponak, Goldman Sachs

Boeing undersupplied the market from 2003 to 2007, keeping production steady, which created a record backlog going into the downturn. Suppliers will need to ramp up, but I think they applaud Boeing for planning this way. Boeing won’t make high margins on the Dreamliner for some time. But that’s priced into expectations, and profits could increase simply because R&D will decrease now that the Dreamliner is launching. Everyone agrees the defense budget is going down. Most investors see Boeing as 50/50 aerospace-to-defense, because that was the mix in 2010. But in 2012 it’s going to be 60/40, and in 2013, 65/35. Historically, when the mix has been at these ratios, Boeing has traded at much higher levels compared with its earnings.

This story is from the April 9, 2012 issue of Fortune.