I originally refused to use anything but a C "steel" blade on my cryostats
(Leica 1800 and Zeiss Microm HM 500 OM) because of the "lip" that is
created between the blade and the blade holder on disposables. "PRO" Using
a steel blade allowed for a continuous smooth surface (we do serial
sections of an entire block). "CON" Steel blades have to routinely be
sharpened (requires additional materials, expertise and time) and
decontaminated if you use human tissue. Disposables are…..well disposable
and you can purchase many more for the same price as the steel blades,
sharpener and accessories.  Both companies have magnetic blade holders that
are a great compromise.  (Make sure you ask  for the right holder if you do
get one since the standard that comes with the cryostat is probably for
regular disposable). There is no "lip" since the blade is held on
magnetically, blades are initially more expensive but wear a lot better
than regular disposables (we did a study and you can get more sections out
of them. Cost ends up being the same) and then they are disposable. They
are thicker than the regular disposable blades so they don't wobble.  The
magnetic blade holders are not that well known. The blades help make
awesome sections. anita