Why are they better? Just lighter and unlikely to corrode?
aluminum is a better conductor of heat so just the material is more efficient than copper. Also the size and amount of tubes going through it is important too, these have a lot of smaller tubes than a standard rad which means more tube surface area which means it's able take more heat out of the water.
I've just been looking at my G40 and mk2 radiators. They aren't the old copper core jobbies used on very old cars but alluminium. Obviously they were manufactured with cost in mind as opposed to the higher efficiency core used in the Radtec ones but they are at least ally. Obviously the end tanks are plastic, but I'll be sticking with my O.E. type one.
Personally I would never pay for a new genuine VAG one, but check out Felgenhaus on ebay. A large German based company, they sell the G40 specific radiators (code no. KVW 092) for £45 plus £15 postage. I'd be interested to see if there was any real difference in the quality between a genuine VW radiator and one of theirs? I bet there isn't.
