From time to time I get asked by parents whether they should buy their child a Mac or a PC. I always reply by telling them to ask themselves which of their friends they can call at 10 (or later) on a Saturday evening when something goes wrong with the computer. Find out what sort of computer that friend has and get one the same. Tech help from a dealer is impossible at that time and their friend with the same machine will probably get them out of trouble with most of the things that go wrong.These days both platforms can do most things, even if one of them does one thing more smoothly than does the other.
Having said all that, your archive does raise a significant issue. I have a friend who has many, many documents written in Publisher and switching to a Mac would be a headache for him. Similarly, as a Mac owner myself (yes, a 27” iMac) I have a number of things on my hard disk that would be difficult if not impossible to access if I changed to a PC. But boy! You sure will discover a whole new world when you move from your Duo to an iMac. Then, just when you come to terms with that, moving from InDesign CS4 to the latest will blow your mind.
Good luck in the argument with your son. I have a nephew who is a computer tech and he is similarly one-eyed. (Not that I am.)