Blue Plum, you need to sift the information you are getting very carefully. The PC and Mac are not the same, they may use the same components in the sense that they both use cpus, gpus, memory, mass storage, internet intervase cards, but that is as far as it goes. The cpus are NOT the same. The Mac uses much higher end cpus in all of their equipment than any entry level PC. When Apple announced it would switch to the Intel cpu seven years ago the president of Intel said at the press conference that Intel was looking forward to a close relationship with Apple developing advanced processors. The Intel processors used by Apple ever since have been much higher grade than normally available.
Three years ago I had to buy a Dell PC laptop for supposed compatibility with my office network. That machine was half the price of a MacBook Pro...but, when I priced raising the CPU, graphics, network interface card, memory, and hard drive to be equal to the MBP, the cost of the Dell was actually greater than the MBP. Yes they both use cpus, etc., but they are NOT the same no matter what anyone might tell you.
The MBP runs very well off an external hard drive...I run my MBP booting to either the internal drive or an external drive on which I have two different versions of operating systems. I also have an iMac with which I do the same thing. Both machines are fast and efficient booting either internal or external. Makes little difference with the fast ports now available.
There is also a huge difference in operation between a PC and a Mac...the PC takes between 15 and 30 minutes to startup, scan for viruses, download software upgrades (Windows is upgraded almost daily) and be ready for me to work. The Mac starts up and is ready in under one minute...not what I call the same.
Final point, you can boot a Mac using either Mac OS X or Windows...the Mac is happy doing either. You can NOT boot a PC using Mac OS X...will not work. So the Mac gives you the option of using native Mac software or native Windows software...an option you do not get going the other way.
Best regards in making your decision.
Ralph