To the best of my knowledge, vendors go out of their way to avoid “apples to apples” comparisons of their products. Various trade magazines, like Storage magazine, will do comparisons from time-to-time, so keep an eye out for that. I think they’re doing a NAS piece in the June issue.
That being said, you can always contact your local EMC and Network Appliance sales staff and request a presentation. You can also visit www.spec.org to get NFS benchmarks for both solutions.
All in all, most of this information is largely worthless without trying a product in-house, on your network, with your processes and procedures. On any given day, any vendor’s storage solution will be better than the next vendor’s solution. What really matters is how it works in your environment.