Only benchmarks I've seen so far are
Macworld but I'm sure there's others out there by now. Not related to Pro tools performance but it will give you an idea. As the test system they use incrementally changes over the years its harder to judge performance for machines that far back but I think they were 15-30% faster over last years models.
Ignore the comments about 'not being worth the upgrade' - if your on a 2006 model (as I am too), you'll see a huge leap. People who brought last years model don't particularly need the upgrade but just because there is a new model, they feel they must state to the world thats its not worth their while - incremental updates never are mean't for these people!
Personally, I'm very tempted by them but might hold out for a new imac when they come along - MBP's are not cheap and for the same money you could get desktop class components and more screen.
If portability is key, then I doubt you'll get much better right now