I also posted this question on the Windows Forum, but didn't receive any responses. I am replacing an old sliding glass door with a Marvin sliding glass door. I am getting the "French" style of sliding glass door which has wider stiles and taller bottom rails than Marvin's (less expensive) sliding patio glass door. I am trying to decide whether to choose the Douglas Fir upgrade or stay with the standard Pine interior. The cost difference is about $400. Is the Doug Fir worth it? Or is the Pine just fine? Is the difference between them just in appearance? Is the durability of Douglas Fir that much better than Pine? Any advice or recs would be appreciated. TIA.