I’m in the same boat as you are with regards to long-term PC usage and knowledge. I’d lose too much time and productivity throwing away all that knowledge and trying to start from scratch.
If you already have PCs, the software you need, and are a knowledgeable user, switching doesn’t make sense from a cost-benefit perspective, IMHO. I know someone else is paying for the computers, but are they paying for the new software, the time you’ll need to learn the new system, lost productivity from not knowing all the little tricks you know now, etc.? Plus, it seems to me that even if your company is paying, you could get one heck of a laptop for the same amount they’d pay for a new Mac desktop and laptop.
On a side note, I’m about to be flamed terribly by the Mac people for posting this, and I imagine you will be too, for considering PCs.
Having been in the same boat, I found the switching learning curve to be vastly overestimated.