ive had the rhino, heavy duty, clamp on roof bars. "square type"
I had my custom roof rack mounted to the feet off the rhino system.
I can say that while they are stronger and have the ability to have any number of accessories attached to them. they are Bloody noisy!!!
I even went and bought some more rubber, the ones that you get for the top of the bars, and put it underneath to help drown out the noise. Hell i duct taped the plastic ends and filled the holes with backing rod to try eliminate the noise!!!!
Point of my ramble is, The weight rating on the clamps is slightly less then the riveted "track" type system.
i chose them because it was cheaper and suited my needs until i got a canopy and i moved my roof rack back. If i had no intention of doing what i did this time again id go to ARB and buy their rack which is fixed to the roof, No other systems are used and while they are expensive theres enough stores around to fix it!
this is the rack 'clamped to the roof'