i have found that my geekbench score was more snappy and my system is slightly snappier.
I think since leopard was meant to be running on GPT and not MBR it performs better.
I have noticed that even vista performs better on GPT.
I also think that MBR is just old and need to retire. same with BIOS
Can't say I've notice any difference.
You wouldn't think it would matter much after booting since its just a partition map scheme. You're still running on the same filesystem.
Could any differences be more related to PCEFI rather than GUID itself?