Yup, nobody will tell you anything specific about their ARBs, so you can only go on a rough theory.
H&R, Eibach and Whiteline favour the x% increase over stock method, so still have a bigger front than rear with S/M/H adjustability and higher tensile rates. It matches stock on the same settings i.e. will eventually understeer, so you set the rear progressively harder to get neutral or oversteer.
Eibach and H&R will most likely be the same bar, they share everything else.
US manufacturers favour matched bars front and rear for a more neutral set up when both set to the same S/M/H.
Hollow ARBs are much lighter and therefore made out of much higher grade material. My Autotech ones weigh 4 and 5 pounds rear/front respectively.. much lighter than a solid bar as you can imagine.
Bigger isn't necessarily better, particularly on a road car or track with big gradients and cambers, like the 'Ring - some body roll can be a good thing, it makes the car more progressive and stops it skitting around on bumpy surfaces.
