One should always know Their History before making any judgments; or before getting even impressed by any 'Marketing achievement' stunts!
Well, it seems that ERSA (in the pre-war Berlin, during the very early Twenties) was the first company that ever built a production soldering iron, in worldwide scale; yes, the first one, ever! Weller, instead, was founded much later in time, during the early Fifties, by some homonymous 'American investor' in the bankrupted and in an extremely very fast pace developing Western Germany of those times (right after the Marshall Plan and the Mutual Security Act that took over the 'business')...
So, the innovator among those two companies above was not Weller, by any means --thus the big difference between their products.
I'm sorry but I am not a fan of Weller and their technological or marketing acrobatics...
-George