Mine is '70s yellow because that's when I bought it! My bet is the newer ones have stronger motors than mine, but mine still does everything I need it to just fine.
If I were to buy a new one, I'd get the bigger one where you raise and lower the bowl. Mine has the head that raises and lowers, and I would just like to have more room when I am adding flour. (I don't recommend getting the plastic shield they used to sell for flour; I prefer wrapping a kitchen towel around the mixer and bowl.)