Well, I have had about all of them, Round bar is the best IMHO!. I currently have a 15,000 lb unit from Valley Tow Right and love it. Something else you may want to add to the one you tow regularly is stabilizer bars. They make a huge difference on long hauls as well. I have a 15,000 lb receiver and 14,000 GVW trailer that sees max on occaision. When I put my weight dist hitch on, I was backed down a grade, it rained and got sloppy. When I drew the weight bars up, the rear tires just spun, when I let them off, I drove right out! Tells me that they work as it was taking weight off the rear axle. Of course it was empty, so it REALLY took it off the rear axles!