My vote would be for the PC... as you note, for the greater number of programs, downloads, classes, etc... available.
When I have taken classes at ZDU {now Smart Planet) the MAC folks always seem to need extra assistance locating resources, [for instance fonts]. There is always someone who knows where to go, and the MAC folk stick together better, too, but it seems undue hassle to me.
Many programs being developed on the web and available in beta for free [like fractals] will not be out in MAC for ages. It will be years before they are more than free, some of them. Many are great fun, and very useful. And, often, they are much cheaper than the "boxed version" when they go alpha, at least for awhile.
The web is great fun, and a heck of a learning trip. I say, "Get the conversion card for the job, and have a great time, too!" Too much work and not any play,
:-) ...do you drive your car only for work, and walk to the bowling alley, or walk off fishing on vacation?