Yes they are somewhat different now but they are still very well built and I have no doubt they are still bullet proof, plus they are backed by one of the oldest names in the industry. Eaton compressors are decent quality and compared to all the outright JUNK that has been sold in the last 20 or so years by outfits like Campbell Hausfeld and a bunch of others they do seem to be impressive. That however is comparing apples to oranges and when you start comparing with the Quincy's, Ingersoll Rand (the T30 series not the Mchome store variety ingersoll), etc then the Eaton is only average. Also the idea that all the old stuff was better is not necessarily true either and just because a compressor is newer and takes advantage of new technology does not mean it is not as good as the old ones.
"well look at the new cars to the heavy duties of the 50's"
Well Ok let's do that, some of the really good stuff that the manufacturers from the 50's have taken from us. There was those absolutely fantastic vacuum wipers and the sizzling hot generators that were replaced with alternators. I really miss those tube radios and other fine amenities that were available, along with the really great air conditioning that was so popular! Oh yeah lets not forget those wonderful mechanical brakes and the REALLY high quality tires that along with the wonderfully engineered suspension made them handle so great. Detroit has really taken all the good stuff from the cars and today there is not much left so yeah you are right, they sure as hell don't build them like they did!
Now about the body styles of the fifties, that is a whole nuther story!