I've found a supplier in the uk of pukani rocks and I do prefer the aqua scaling potential with the pukani as they seem to fit together more natural looking. Where as the caribsea rocks look a bit blockier like bentreef says.
Cafereefs looks great though and quite natural, my only concern with pukani is leaching phosphates, but if I acid dip them and let them soak for 24hours in water they should be fine and I can use some phosgaurd during the cycle to remove any thing that leaches during the cycle??