I personally would sash them... this way you don't have to worry as much about the points being absolutely perfect. They aren't quite as noticeable with a solid color in the corners... I like the less stressy way to do anything.
The sashing will also give it a kind of modern looking twist to it instead of scrappy - not that scrappy is bad cause it isn't. I guess I like it better with the sashing between the squares for some reason. I'm in the minority lol.