It usually comes down to the apps. Do you want Final Cut Pro? 3D Studio Max? Many apps are cross-platform, but some aren’t, so you have to choose the app before the platform in a lot of cases. In the 3D scene, a lot of plugins aren’t available for the Mac — 3D is heavily Windows.
In terms of costs, it’s almost always more expensive to switch than to stay, because you have to buy for the new platform, so I don’t counsel people to switch, generally.