Couple points should be clarified: 

• mac software is not more expensive than PC software. It's the same price. Please show  me where, because I've not seen a single mac prog that was more expensive than its PC counterpart. There are, however,  fewer utility programs compiled for mac (Texture Converter for example). But as mentioned, in a dual boot and / or virtual environments such as VMware can solve that.

• While I admit that most newer macs aren't 64 bit, I don't agree with the claim that PCs are more flexible or more powerful than mac. I'm not sure what the basis of the claim was. As far as the "upgradable" comment , just keep in mind that you'll never have to deal with OS / driver incompatibility issues because it's pretty well integrated.

Just to give you an example, I'm using a 15-month old Intel Imac v5.1 running a 128MB ATI card. This is the best part: the Imac is the processor and SECONDARY monitor - the primary monitor is a 26 inch Sony LCD TV. No problems here, no need for upgrades. 

But to answer your original question, pz3 (et al) files are platform independent, so you will have no problems using your Runtime on a mac. I created mine on a PC over the course of eleven  years and I can use anything in it on a mac.

Oh yeah, underneath the mac GUI is UNIX, an extremely stable OS which has been under development for nearly 40 years. I've crashed the system maybe once since I switched.