So what type of steel are you going to use and what thickness? Also, how are you planning on finishing it....paint, just clearcoat?
I honestly think that using something like 14ga 304 stainless and leaving it unfinished would be the best looking and most rugged. I would pay extra for that.
Also, I think four bends is the only way to go. Don't really need to worry about welds/gaps in the corners as long as the cuts are good (i.e. laser or plasma cut). I think the U-shape would look awful and cheap in comparison.
EDIT: I just noticed that you are planning on 3/16" thick steel...I'm interested to see how this turns out (I think it will be a bit too thick). Just so you know...the dimensions you listed with a 3/16" thick piece of steel will weigh in around 3.2 pounds.
Maybe I'll throw something together in Solidworks at some point.