You have tried a number of times to get an answer to this Q so I will offer what little I have.
In the end the difference may depend alot on what you are trying to accomplish. The top dog insiders at NI that could answer this off hand have been tied-up for a while.
What I suggest you do is get in contact with the local NI Rep and tell them that you want to talk to who ever does the bench-marking of the LabVIEW Challenges. I believe they run the challenge candidates on multiple platforms and may be able to supply some numbers to get you started.
If you look at the results of the "Bit Twidler" challenge at the URL
http://www.ni.com/devzone/lvzone/codingchallengearchive.htm
They mention using different architectures.
Please let us know what you find!
Trying to help,
Ben