Yea, this is the problem with Pella. They just design stuff the way they want and never consider the finishing process. Whether it is stained or painted, unless you are always very careful (which nobody is) you will eventually scratch up the paint or the stain. Overall I think a properly poly'd surface is more durable than a painted one, but paint is easier to touch up, so I think it's about even which ever way you go. Don't you want that door to match the other trim in the room?

The convention is, you paint the edges and faces etc, the same colour as the trim in the room it opens into, and, as mentioned, stain surfaces visible in the kitchen, when the door is closed. As for the mixture of wood/mdf framing, why bother? If you're going to stain one side, that overrides the other concern- just prime and paint the dining room side you don't want to stain. MDF is only used for painted door jambs etc in place of 'real' wood because it's cheaper, doesn't have knots/flaws etc.

I've also painted old stained trim with no regrets. I did not strip it all (tried at first, but it was very aged and too difficult even with chemical strippers and heat guns!)- I simply sanded and used high quality Ben Moore primer and paint with excellent results. I personally much prefer white-painted trim to stained, UNLESS the house is of unusually high build quality. I come from a family of architects so am probably a bit overly-sensitive to proportion and design, so YMMV... but I feel like stained trim really calls attention to each element: doors, windows, baseboards, crown moldings are all brought into high contrast with stain and their placement and proportions become important design elements in a room. If they were well and thoughfully designed originally, that can be a beautiful thing. If not -I'd paint them. Our last house was a 1926 Foursquare. it was definitely much better built than most homes today, however, it was probably a Sears kit house originally, basically a builder-home from that era. i.e. not architect-designed like the previous Victorian I'd lived in. It had stained fir trim (with nice details) throughout, and DH and our friends thought I was crazy to paint it. Guess what? The house looked SOOO much better after I did. It actually became a much classier-looking house. The dark wood around doors and windows -which had been placed pragmatically rather than for aesthetics- made the house seem a bit akward. The white paint allowed the really GREAT elements in the house, like it's gorgeous birch floors, ample sunlight and great "flow", to really shine. Just my 2 cents!

I am doing the same as DLM. Mahogany door stained on outside and inside. My interior will have white trim. Wood floors and some stained wood stair parts, and other wood accents to pull it together. Or you can paint your interior door.