Posted for <daveleonard@cox.net>:

Good point bill, there are lots of other important factors.  But this disussion is about thick vs thin.  Metal, coolant, air , and fin qualities have to be judged separately.  I am assuming these qualities are the same thick and thin.  As far as delta T being smaller for thin rads, you miss one of the main points in the example above.  Slow down the air in the thin rad and it collects the same amount of heat that the thick rad delivers.  No matter how thin, slow down the air enough and the delta T is the same.  All factors can be set to the same - coolant heat loss, delta Tair, mass of intake air, weight of the radiator etc.  The only major differences are speed of the air and thus the drag of the air through the rad.

Dave Leonard