Welcome to the forum, Steve.
Not much to add to the comments here - everything above is good sound advice from those who have used these machines for many years. I do not have a PM lathe, but my Eisen 1440 is nearly identical to the PM 1440GT. Both are Taiwanese with very similar features. The most significant 'plus' on the PM is the larger spindle bore; on the Eisen, it's the heavier weight. With the equipment you're considering, the good news is that it will be nearly impossible to make a mistake. Both lathes and mills you're considering are great machines and as has been pointed out by numerous responses, service from PM is incomparable. The only reason I went with an Eisen over PM is because I got a steal of a deal in December on a close-out. My opinion - weight makes a difference. I'm purely a hobbyist, but I've used both heavy duty machines and some lighter ones (both mills and lathes). To me there is a notable difference in results with the heavier machines. But again, that's only one rookie hobbyist's opinion. I would be inclined to pay considerably more attention to the counsel of our seasoned veterans.
The biggest 'me too' I'll offer from one who has not accumulated a lifetime of tooling is the cost of tools and other peripherals. It can get very expensive very quickly. I have learned two things with regard to these expenses: 1, don't be afraid to buy used. Sometimes used tooling is out there that is, for all intents and purposes, new but at significantly reduced prices. And 2, listen to the experts. If you see something on ebay or craigslist that seems like a great deal, put out an APB here at Hobby Machinist. You're guaranteed to get some of the veterans here that can give you guidance on whether it's a good deal or something to avoid. I've had BOTH happen - snagging a steal of a deal, as well as, dodging a bad deal.
Again, welcome. And you are to be commended for picking a hobby that can facilitate your son's activities professionally.
Regards,
Terry