imho, The apple machine is going to offer you protection from spyware, virtually no crashes, and a really pretty GUI..OS X as an operating platform is really common sense based, imo, and a hellavu lot less covoluted than windows..but is buying an apple going to make you a better designer?..no..so if you want cheaper, go with the upgrades or even better a new pc..
holla...
(see i'm objective..cuz I use an ibook for all my shiznit..)
^O^ "steve jobs aint' got shit on me!!1"