Mitered frame ends vs butts

[MMC757]

Forgive my newbness if the answer is common knowledge...

Is there a structural reason to use mitered corners in the frame vs butted ends?
I know the correct angles would still need to be cut for a tapered frame, and the open tubes would probably get capped, so the work saved would be minimal to none, just wondering if there's a structural reason to do it one way or another.

 

[HenrysT]

I don't know which plans you are following, but the CCR plans have the front round tube cross member fit into a notch and the top and the bottom sides of the rectangle tube main rails are rapped around the front cross member. The kick ups are mitered and if I was doing it again, I would fit 3/16" flat bar to the inside of the rectangle main rails, plug weld it in and slide the mitered piece in and weld it without fear of burn thru. The rear cross member could be mitered or notched. Some people like to run their wires etc, thru the frame so all the weld joints will have to be considered. I heard that longer the weld joint the better. I guess it spreads the load over a wider area.