Java HotSpot Virtual Machine

Hi,
I had recently read at the microsoft claming long back
the VM created by them were the best for the window
environment.Is there any one who has used that and
found the difference in performance.I would appereciate
if someone from the sun let me know about there
evaluations(sure they must have done).
I believe there is the jvm created by the ibm,if it is
there how about its performance.
vickyk