Right now I'm currently running PT9 on a 2008 Macbook Santa Rosa with 4GB 2.2 GHz Intel Core 2 Duo and am looking into getting one of the new MBP i7 quad cores. I can't decide whether or not to go with the 2.0 or 2.2 GHz. Will it make a big difference in speed? I don't really need the graphics upgrade, and will have 8GB of ram. Thanks.
Didnt have time to wade through the comparison but have a look here: http://www.primatelabs.ca/geekbench/mac-benchmarks/
You can install the RAM yourself. It's very easy and can save you over a hundred bucks. The difference between 2.0 and 2.2 is minimal, considering the difference in price. Instead, you could opt for the 2.0 one and do the RAM upgrade yourself. (check out http://www.ifixit.com/Browse/MacBook_Pro for instructions on how to install the RAM)
From what I've read, RAM will make a bigger difference than CPU speed, so you probably wouldn't notice much difference with the 2.2 GHz. If you can afford to, why not? Keeps your machine futureproof for longer!
Other people might chime in with their own experience too, but that's what I've read for the most part.
The big difference is between i5 and i7, i7s are far better in so many ways. for music purposes just look for a good CPU, RAM (the faster-greater Mhz the better) and the screen size you are comfortable with...
oh! i almost forgot! usbs, firewires, and connectivity is also a big issue for "music laptops"