Crayford focuser vs. rack and pinion

I am about to rebuild my 8" f/7 to be a little lighter (so I can replace my
Cave mount with a Losmandy GM-8),
and to use a 2" focuser. I am also looking to go for a lower profile
focuser, so that I can get the diagonal a bit
smaller. Can someone explain to me the pros and cons of Crayford focusers?

It appears that the big wins for the Crayford are much lower racked in
height, and zero image shift while changing
focus.

I don't see any 2" rack and pinion focusers that have 1.5" racked in
heights--but there are plenty of Crayford
focusers that are in the 1.5" to 1.6" range. On the down side, along with
low profile you get your choice of
either relatively small travel (a problem for doing astrophotography, where
you need a couple of inches extra
travel to get the focus inside the camera), or a lot of penetration into the
tube when you have the focuser all the
way down (probably not a big problem, since the tube is 9.75" OD, so the
first 0.875" isn't even intruding on
the mirror, and even a little intrusion probably won't affect the image
much.