here is a comparim of their 2 most important zoom
the 28-70 f2.8 and the 70-200 f2.8 range,
compare the price, but keep in mind the AFS vs the Screwdriver lenses..
Pentax
Zoom Wide Angle-Telephoto SMCP-FA* 28-70mm f/2.8 Autofocus Lens
979.95
Zoom Telephoto SMCP-FA* 80-200mm f/2.8 ED IF Autofocus Lens
1299.95
Minolta
Zoom Wide Angle-Telephoto AF 28-70mm f/2.8 G Autofocus Lens
1029.95
Zoom Telephoto AF 80-200mm f/2.8 APO G Autofocus Lens
1249.95
Nikon
Zoom Wide Angle-Telephoto AF-S Zoom Nikkor 28-70mm f/2.8D ED-IF Autofocus Lens
1369.95
Zoom Telephoto AF-S Zoom Nikkor 80-200mm f/2.8D ED-IF Autofocus Lens
1419.95
Zoom Telephoto AF Zoom Nikkor 80-200 f/2.8D ED Autofocus Lens (with Tripod Collar)
899.95
Canon
Zoom Wide Angle-Telephoto EF 28-70mm f/2.8L USM Autofocus Lens
1089.95
Zoom Telephoto EF 70-200mm f/2.8L IS (Image Stabilizer) USM Autofocus Lens
1899.95
Zoom Telephoto EF 70-200mm f/2.8L USM Autofocus Lens
1169.95
I guess the price is different but ain't that much anyway