I'm not sure I can give you a definitive answer, but I can give you information which might help.
First, maybe a little understanding of how paintless dent repair (PDR) works. Basically, the repair person finds small holes in the vehicle where they can access the panel they are working on with long, thin tools, which have a variety of ends on them. They insert the tool into the holes and find the place where the dent is at in the panel they are working on. Then the put lights/mirrors in the area of the dent so they can see the extent of the dent through reflective means. They will then use the the inserted tool to press the dent out. They'll force it a bit past "flat" so that the dent will form back and stay where they want it.
Most dents which are hail dents can be fixed through PDR, but with that comes caveats. It usually isn't the size of the dent which makes the difference, but rather the type of dent and where the dent is located.
- If a dent occurs on a corner or edge (ie: a fender crease), it isn't a candidate for PDR. The PDR repair person cannot recreate the crease. This has to either be fixed by hammer/dolly and repaint (probably with a touch of Bondo) or replacement of the panel.
- If the dents occur in the roof of the car, PRD becomes problematic because this area of the car is hard to get to without a lot of dismantling of the inside of the car. This is also probably the worst hit portion of the car (in most cases), so it's a double whammy, I guess.
- Any place where the dent occurs on a seam or where there is bracing becomes problematic, because the tools which the PDR repair person uses to fix the dent cannot get to those areas.
- Is the dent you're looking at just a dent or is there other shapes in there, too. Any crinkles or other than the dent itself? Crinkles of any kind cannot be fixed through PDR.
- Obviously, as you stated, if any dent comes with paint issues, it cannot be fixed by PDR, either (I think it kind of implies it in the name, but thought I'd add it, lol).
Something else to consider when looking at PDR is, many of the dents will pop themselves back out under the right conditions. The big "if" on that is whether the vehicle can be left to sit in the sun for a period of time (like all day). Metal has memory. When it is dented it becomes stressed. When the sun heats it, a lot of those dents will come out because they want to get back to where the memory tells them to be (the destress and pop back to normal). Consider this before getting PDR. Why do I say this? Because PDR is not cheap. When I was working around it, it cost about $50/dent ... that can add up quickly.
One more thing to consider ... you can always take it to a PDR person (or have them come to you) and ask for a quote and whether they can fix the dents. If you take it to a body shop, they may have a PDR person and can give you a quote. Just because you ask for an estimate does not mean you are obligated to have them repair it. If you go to a dealership, they might be willing to give you the name of their PDR person, but probably not. And, if take to a dealership to have them fix it, you can bet they'll just call their PDR person and then they'll tack on to the top of whatever bill the PDR person comes at you with. (If you cannot tell, I don't have a high opinion of dealerships. Having worked as a car salesman before, I can give you plenty of reasons not to trust them.)