yes is true macs don't do better at graphic design but a reason macs became a standard for graphic design is their display consistency. yes a windows laptop can outdo macbooks in screen resolution and contrast ratio but macs display colors accurately and consistently with all their computers so files sent to office A looks exactly the same as files sent to office B. (with that note, stay away from samsung monitors).
plus if you are a designer, your living is dependent on convincing clients that "design matters" and preaching that word while working on a plastic windows computer is just hypocritical.
Bah! Color calibration has always been a crapshoot. I've been in the industry for almost 20 years - believe me.
Besides, any good quality monitor will let you calibrate so that colors are consistent from screen to print. Viewsonic was a leader in this area.
Plus, there are lots of nice cases that you can buy for PCs. It's a common misconception that design is just about making things look good - I know lots of designer who think so and they are wrong. Form always follows function.
OSx86 on a laptop is probably not a good idea because you're not going to have the right hardware.
There are plenty of laptops that can run OSX. Just look at the compatibilty list on Insanelymac.