Smart Trim is all we use in my part of Canada; in fact, we also rip the 5/4X8 or 6 down to 1X1 actual for our inside corners. We paint the raw edges and in your situation where they are all butt edges I would do the same.I just installed a new bay window in my home.
I would like to trim the exterior with LP Smartside trim. It's basically 1"thick plywood with some kind of coating on the front (cement?) and is available in standard lumber widths.
The reason I would like to use this product is for ease of ripping and machinability.
All of the raw edges will be hidden or butted against another peice of trim, the window, or existing stucco. I would, however, like to finish these exposed edges prior to install. Any suggestions?