What are you using now? an iMac has limited upgrade options and shorter shelf life.
You can run Windows 7 on any PC and have your picks of graphic setups, SLI, CF, higher clocked RAM and cpu.
A boss gets to decide. And for same $3,000 per seat plus software, cross-platform license....
You can run Windows on your Mac but... there is total lack of real fan + thermal control so that does not work well in long run.
And your boss probably doesn't want to wait on Apple or buy into higher cost proprietary technology or 3 yr old design.
Haswell PCs? Unlikely they want Xeons.
Software? good use of cores? probably Windows.
Best Windows laptop: MacBook Pro 13" (but heat again is the Achilles heel)
Security: Mac
Hardware support and reliablity: Mac
Dealing with firmware updates: Apple tends to issue very few, usually one more after a model ships, PC: tend to see much more that you need to deal with and can be PITA and necessary, esp. with motherboard and processor support with new line.
Make a spreadsheet and list all the things you can come up with and see for yourself.
I don't think you'll win over your boss and how does it make you look? team player? reliable? dispensable?