Eventually I decided on mitered corners with two contrasting splines in the base and one in the top, which would be attractive and reasonably strong. I have a shop-built miter sled for my table saw, which makes nice miters, but the saw doesn't raise high enough above the sled to cut miters in 3.5" wide stock, which is what I'm using for the boxes. I've made up a couple nice samples using the router table and a chamfer bit, but this takes too long and requires a lot of fiddly set-up.
Anyway, to get to my question, do inexpensive miter saws, like, say, the Delta 36-075, make an accurate enough miter for this purpose? I'm considering trying this, since I think I can justify the cost of the saw because of upcoming extensive work on the moldings of my beat-up old house in the near future.
I'll be grateful for any opinions, and thanks.