I have done an evaluation project for a Danish TV station trying BOTH....
Here are the results:
Discreet Combustion: Works well, allows for inclusion of the Discreet Color Corrector. However, any
very difficult keys (some shots had incorrect chromakey colors/lighting) required significant adjustments and effort.
Ultimatte (AE version, which worked as a Plug-In to the Discreet Combustion:) Works excellent:
the speed and ease of use were simply fantastic: Click key background / Mix / Done ! Ultimatte
also includes the Grain Killer feature, which was very nice to reduce noise. Only thing lacking was
extended color adjustment, which we easily achieved back in Combustion....
Summary: If you need speed and have the bucks, get BOTH: Combistion, as well as the Ultimatte Plug-In for Combustion.
However, If you don