See Powermatic PM3520 Tips, Reviews, Sources, Links at:
http://woodturner.org/vbforum/showthread.php?t=1839
Look under "Reviews" for an excellent list of differences between the a
and b models. There are a lot of "nice" little changes, but little
that is earth shaking.
Maxprop wrote:
I've just spent half an hour with the archives in an attempt to learn the
differences between Powermatic's 3520a and b models. Can someone help me
with that?

Thanks,
Max