I'll second a grout line, but 3/8" is too big for this on the corners IMHO.
It would add to the cost, which you may not want to do, but you could dress it up quite nicely if you used some tile edging profiles like those from
www.schluter.com. Rondec is nice, but the thing that really adds is not that, but the corners. You can miter the stuff, but it will leave a sharp edge. If SS was you choice, you could probably smooth them over . The anodized aluminum would show the raw aluminum color if you cleaned the cut edge too much or rounded it over. They do have profiles in plastic, too.