The Yuba Mundo is definitely heavier because it's built using high tensile steel and uses much more tubing, just check out pictures. The Sun bike is CroMo steel, the same as the Big Dummy. High tensile steel is weaker than CroMo and you need about 2x of Hi Tensile steel to get the same strength as if you were using Cro Mo steel.

If I'm correct the Mundo frame itself is over 30lbs compared to 15lbs (including fork) for Big Dummy. I expect the Sun bike to be slightly heavier than a complete Big Dummy but still way under a complete Mundo's weight. I'm guessing that a complete Mundo is probably close to 50lbs (the weight specs are hard to find), complete BD is just under 30lbs and the Atlas will probably be another 5-10 lbs heavier than BD.

And for business I'd much rather get CETMA bike or heavy duty trike (depending on how heavy my loads would be and how far I'd have to haul them) than a longtail.

I agree though that the Sun bike seems like the way to go if you're budget oriented. I was very excited about it, but when the new BD frame came out and it was much cheaper than I expected I was too impatient and bought one. Like I said though, I don't believe Sun will market their bike the same way Yuba and Surly do. The Sun brand lacks the coolness factor of the other two, they've build heavy, boring industrial bikes for years. They'd need to work on their image and reach the right crowd for their bike to succeed and present a significant competitor to Yuba and Surly.

Also one thing that turns me off from Mundo and the Sun bike is that they're "one size fits all" and I always had issues with frame sizing. I'm 5'11" and I should be riding 18" bike but had to get a 22" BD to be happy with it. A 20" bike feels too small. I was afraid Mundo or the Sun Atlas would feel too small for me.