I've been experimenting quite a bit with my new macbook pro and have run into significant performance issues with VMWare fusion as well as running natively from bootcamp.
My three scenarios are:
1) Native booting from bootcamp (16gig, SSD)
2) Native booting OSX, VMWARE fusion running from bootcamp partition (8 gig ram for vmware plus 4 of out processors)
3) Native booting OSX, VMWARE fusion running from files on native OSX partition (SSD) (8 gig ram for vmware plus 4 of out processors)
I don't have enough space to try all these at the same time but I'm suspicious that number three is significantly faster than either 1 or 2.
I've found that in both 1 and 2 (which is what I have loaded now on my computer), doing things like building large projects with visual studio 2010 boggs down, where as on my Lenovo W520 running on the same type of SSD, I don't get bogged down. I am surprised native bootcamp is any slower, but it seems to be.
Any thoughts appreciated.
Native boot has always been faster for me (understandably, with no abstraction layers)
As for the other two, there shouldn't be much difference. Windows is still running through the same abstraction layer, so if the same amount of computing power is available then they should be comparable. If one is on an SSD, that would explain some of the speed difference.
On the one running on top of OSX, does it slow down when you do a lot of processor-intensive tasks under OSX? If so, it's the SSD making the difference there - but it still shouldn't be faster than VMWare.