The pro mac 800, 850, etc are metal saws. They are much more modern than the other 80 cc saws you mention. They are lighter weight and share some parts interchange with readily available 10 series saws, they take the same clutch, bars, and some other parts. They also have automatic oilers which many of the big old saws don't. (although the super 250 does have auto oiler.) In addition, as Mark H would say, they have lots of "snot". Even though they were made in the 70's and 80's their performance is on a par with todays saws of the same size. I would not discourage you from getting the older saws, but if you are going to use it frequently the pro macs are a better choice. By the way, you want a pro mac or super pro. If its called power mac its likely a cheap homeowner saw.
Jim
