I believe that airtec intercooler has simply the best price/power ratio.
Maybe SpecR I/C is better but I believe that you can't see big difference on an engine with up to 500bhp.
Size does matter!
A big I/C is not always a good solution, you always have to consider what's the best for your engine specification.
For example on my car with a T35 and 630cc injectors I've installed an intercooler from Airtec Rs500 style with 60mm size. If I have installed a bigger one or a SpecR then maybe (I haven't tried it) peak bhp will be raised but all my graph on torque side and spooling time should be worse! So why to compare 2 products with different size and price between them? Each of them is for another engine specifications.