How much RAM do you have (you mentioned planning to get 5G which sounds sensible but how much do you have now)? OS X has many strengths, but being frugal with memory use is not amongst them. The standard 1G on Mac Pros is a complete joke and useless if you're going to use Parallels seriously. RAM is usually the biggest bottleneck - if you start to run out, the computer will start thashing the discs, and adding more RAM will be much more effective than trying to speed up the discs...
At a guess I'd say that IE starts faster because most of its components get loaded when the OS starts up, and the IE "application" that you launch is just a shell. Can't say that I'd noticed any night-and-day difference with general browsing but I'd concur that IE7 in Parallels vs. Safari in OS X feels a bit slicker at some things (like Google Maps) but this is more likely to be due to differences in the scripting engine (and probably authors optimising their AJAX code for IE). I also suspect that open source software (Safari is partially based on open source) that runs on multiple OSs and CPU types doesn't really have a level playing field against single-platform, closed-source products which can be hard-coded for a single OS and dump lots of extraction abstraction and modularity (especially if it plays fast and loose with web and net standards!)
...none of this is likely to be changed dramatically by using a RAID setup.
And, since I'm not employed by Apple, I can safely say that if you have a big investment in time & familiarity with specific bits of Windows software, you shouldn't switch to OS X just for the hell of it.
Last edited: Oct 26, 2007