I'm surprised anyone would pick a Nikon over Canon for macro work. The MPE-65 and electronic first curtain shutter combination is hard to beat.
Your surprice surprises me!
If you think the MPE-65 is the greatest macro-lens ever made you need to look a little further.
What about Macro-Nikkors, Printing-Nikkors, Apo El Nikkors, Ultra Micro Nikkors, Zeiss S-Orthoplanars,
Zeiss S-Biogon, Zeiss Luminars, Coastal optics, Apo Lanthar 120, etc. etc...
The new Canon is very good at it's price, but there are far better macros out there.