I use 1" & 1.25" DOM tubing mostly in 0.065" wall. I do have some heavier wall tubing but as I remember back from naval architecture school, the way to decrease weight and maintain strength is to minimize wall thickness (or plating in a boat) and increase the depths of the supporting stringers and frames. I am NOT an engineer so let cosman walk with that one.
I also use those sizes because they match the bending dies I have for my hydraulic tubing bender., which is important in that most of the tube work I use is not straight.
DOM welds nice, finishes nice, esp if you are tigging it.
I have use just regular seamed tubing on the CBR because I needed some heavy stock for the shock brace and I had it on hand.
I've never used cromo tubing, mainly because of the cost and the welding sounds complicated. I'm not building bikes to shave the last couple pounds off, I'm building them to ride and have fun. If someone gave me a good reason to use it I would, but so far the DOM tubing has been great and its what most Harley, rockcrawlers, regular racer types use.