The difference is that you use the system-provided glext. When you use the one provided by the official web site, at least on my machine, Eclpse works perfectly. Plus, cross-platform is not a problem - this hack would be enabled only in debug builds. Plus, if it is cross-platform, VS most definitely handles this, and I would find it surprising if XCode didn't work with glew (meaning that if a platform-specific issue comes up, you can effortlessly work in native environment, and use VIM in linux for the major dev effort).
No, I'm saying that defining GL_GLEXT_PROTOTYPES will cause me problems later on, which is why I need a good IDE that I can use that is able to complete arguments via function pointers. Visual Studio definitely works perfectly with GLEW and gives you argument completion, just that any other IDE outside of Windows is incapable of doing so.
I would prefer it if the IDE has support for VIM keybindings too, but if not, I'll still use it over VIM if it has actual argument completion for OpenGL functions.