In the end it all depends on system requirements. When I learned GLSL and realized how much freedom it gives I was firmly set on using it. I also implemented physics in a separate thread so multi-core CPUs became a great bonus if not outright requirement.

This resulted in my target hardware being a Core 2 Duo + a DirectX9c class video card. That's around 2007. While Windows 98 with drivers available to it barely reaches 2004.