The question was not which is better / easier to use, but which is better for product development - presumably with profitability in mind
We produce a software product (commerically) for a bunch of pilots (2000-3000), and is available as a PC/Windows product only. Ditto our competitors. Ditto most software. The market is far wider for the PC, and although biased, development is easier / more resources out there IMHO.
There is a growing (and vociferous!) Mac community. However, starting from the minority viewpoint, tools / software / hardware have been developed (Intel Macs, Parallels, emulators, Wine, Online via RDC) that allow Macs to run PC software. Not a lot the other way round...
So yes - if it is easy write for both - although ensure the average PC dummy can install it. If you have to make a choice, I'd advise PC everytime - and ensure the product and installation are very easy to use - if the user needs to understand the word "file" or "directory" you are lost
PS The Mac bunch will then whinge, as they do
Get one of them, give them the product for free, and write instructions for how to use the product on a Mac via the above methods.