Graphic Design Software for the PC

My company primarily uses PCs, but we have a small (less than 10 people) group that uses Macs for doing graphic design. The support costs for these few Macs is causing management to raise the question of eliminating them. Not being in the graphics design field myself, but having been asked to research this question, I would be interested in hearing from graphics design professionals. Is the software available for use on Windows PCs (or Linux?) equivalent to what is available for the Mac?