I have some pros and cons for both products and my boss wants me to pick one. If you had to pick one for ARM development which would you go with and why?
Cost is not an issue.. company expense.
I have never used IAR so I can't comment other to say that it also sounds very professional. I like the Keil toolchain because I also do a lot of 8051 work so I am very familiar with it. As far as I understand IAR supports other MCU families as well, but I have no idea which. There are lots of free MDK versions that are paid for by the silicon vendors so without knowing your chip it is hard to say anything else.