As a paint contractor, I deal with both on exterior finishing applications, as well as several other more exotic species, in both clear and paint grade. From what you are describing, I would choose cedar. It is generally easier to work with. It is softer, so it takes finish very well, oils in particular. If you do choose cedar, and depending on color and finish, do a little research on tannin bleed. That is the biggest challenge of painting it. Beyond that, it works very well. I put cedar clapboard siding on my own house about 10 years ago and it has done extremely well, much more so than the pine trim I applied with the same finish system at the same time. And the fir door on the mudroom is not far from the last round up.