I'd be interested in a speed test, myself. I'm not sure but I wonder if global variables aren't stored in a different address space than local variables, which are stored...on the stack, aren't they?
The difference in speed between locals and globals in most function calls can be drastic (in a bottleneck function, anyhow.)
The difference in speed between locals and globals in most function calls can be drastic (in a bottleneck function, anyhow.)