Lumber and Siding - Garage Door Trim Replacement

I own a 3 year old house in NE Massachusetts whose window and door trim is already rotting out. The trim in question is finger jointed pine (man, I hate that stuff!!) and must have been primed and painted with latex. I'm replacing the window trim (brick molding) with Apex/PVC stuff. I need to replace some 1" x 5" and 1" x 8" garage door trim. I'm leaning towards using cedar, priming it with oil based primer, and then painting it with latex. I plan to prime and paint the lower ends of the boards where they contact the concrete and probably the backsides of the boards several feet off the ground to prevent water from wicking up the grain of the wood.

Do I even need to bother with oil based primer if I'm using cedar? Or, should I do the oil based primer and top coat with oil based paint as well? I'd like to do this right, just once.

I'd use the oil primer! it will seal the wood better than any latex will. Also if you plan to paint a light color the tannins in the cedar will bleed thru latex and discolor the paint. A good coat of oil primer will prevent tannin bleed issues. You can use either latex or oil base for the top coats.

Quality paints may cost more but will outlast their cheaper counterpart.

Just wondering why you aren't using PVC for the garage trim also? Yeah pretty expensive I know..but it only needs doing once.

I found the PVC brick window moulding difficult to work with. In order to get the nails to countersink properly I had to pre-drill "divots" in the surface. Also, some of the dimensions are close to, but not exactly equal to, the wood moulding I was replacing. Cedar is very easy to work with. And, as you say, the PVC stuff is not exactly cheap.