technically they are all pc's (aka Personal Computers as specified by the name IBM gave it...) but no time for rant..
most of members have brought up great point on where Mac is superior to the PC and vice versa...
it all depends on what kind of user your Dad is...
if he is not of a adventurist in computers and wants something that quote and quote "just works" set him up with a mac...
one of the main reason why most people here choose a pc is because they have a choice on what to choose (or if you buy OEM what computer you want) what parts fit your budget and then at any moment you can upgrade..
unlike with a mac which is sometime a nightmare to do (especially on the unibody macbooks try to upgrade the ram on that thing..

)
and also costly unless you choose third-party upgrades which there you are loosing the guarantee that it just works because apple does test their products (which is the one of the reason they are so expensive [they test any products because they are looked upon as the type of company that "just works"
And while yes DOA's can happen at any moment and sometimes some bad hardware gets through its usually at a minimum unlike with some third party manufacturers...
so to end my post if your dad wants something that works (to an extent of course) and does not want to do any troubleshooting then by all means...
but be prepared to pay a pretty pennies for that reliability and for a comparable Windows PC