Depends on whats under the hood so to speak–I run a custom machine–win 7 64bit, 16 gb ram, nvidia graphics, core i-7 processor, etc. Also a SSD will make a big difference in a PC. From what I understand this is the main difference hardware wise between a mac and pc–its a $75-150 upgrade.
I also have a PC I’ve built myself, and it cost me a fraction of a Mac. Computers crash when it overheats, so if it is properly cooled, it should be ok.
Macs are great because they’ve engineered the heck out of it and support is as simple as going to the Apple store. PCs are a hit or miss. Unless you build your own machine and know what you’re doing, get a PC and save a bundle, if not, get a Mac.
I have a PC at my regular gig but prefer a MacBook Pro for my consulting work, which I do out of my home and a co-working space. I use AutoCad for Mac and Sketchup Pro for drafting and modeling. Artlantis and Phtotshop for 3D renderings. My MacBook has been able to handle all this and I can transfer drawings back and forth from PC with no issues. I have Revit installed on the Mac as well using Parallels on Windows 7. Use this occasionally for working with others models.