It's a computer
If you have to convince somebody to choose a Mac vs. a PC, then you're placing the answer before the question. Ask the person what he or she wants from a computer and then guide him/her through the process with objective answers.
I use both Macs and Wintel-based PCs. Aside from occasionally forgetting to use the Apple key or the Alt and Control key, as appropriate, I don't know of any significant difference. Windows XP is a fine OS

and all of the software I need is available; Mac OS is an excellent OS

but all of the software I need is NOT available (btw - I don't mean games).
And given the price difference between Dell, for example, and Apple, I continually have to
convince myself to remain a Mac buyer. (I've been using the Mac since 1988.)
Consumer Reports rates Dell and Apple as the top 2 personal computers, so you may have your work cut out for you. Good luck.