Trim and Siding Order Question – GreenBuildingAdvisor

I’m working on an exterior remodel of an old 1940’s house in zone 6B. We are removing old vinyl siding, the putting up new housewrap -> some new windows -> 1.5″ rockwool insulation -> 1×4 rainscreen -> extension jambs -> 1×8 horizontal lap wood siding.

The most common method seems to be installing trim first, then butt siding to it and caulking the joint. A “modern” variation of this I’ve seen is to skip the casing, and just butt the siding to the extension jambs.

The other option is to do siding first, then trim on top. This seems less common, but I like the idea of not having exposed butt joints. The downside would be small gaps behind the trim caused by the siding profile.

Is there any strong argument for or against either method? I’m most interested in maximizing durability, but I’m also wondering if either method is easier to get right for a non-professional. 

Thanks! -Glenn