Hello
I have used both sets of software to georeference aerial photographs. There is really no difference in the quality of the finished product. As Robert said, the quality of the data that is being used for GCP's, the quality of the data being georeferenced, and the quality of the GCP's themselves is the major difference maker.
PCI Geomatica is specialized remote sensing software that is used almost exclusively with raster data. You can georefernce, mosaic, orthorectify, and add/drop bands in the software on multiple photographs. The processing time, at least I found, is a lot faster in PCI Geomatica.
I had to georeference a couple hundred air photos, and I used PCI Geomatica, mainly because of the large number that I had to georeference and the availability of the software to myself. I guess it really comes down to a users choice, but both sets of software run on the same principles when georeferencing.
Hope that helps
Andrew