PC or Mac?

[~Coxy]

That's a generalisation and an incorrect one.

You can upgrade anything in any Mac except for the CPU.

And with a Mac Pro, you have more expansion and upgrade options than you'll ever need.

You can't touch the graphics card in any Mac except the Pro. You can't upgrade the RAM in the Air. You can't replace batteries in any of the new laptops. You can upgrade the RAM and HDD in the mini and the iMac, except you need special tools to open them in the first place.