When you buy Prepar3D in one of it's flavours you get it "for free", as it is included among other payware aircraft. I found that the JF P38 is a bit excessive on the frames, which might be because it's a port over.
I also think the FSD version has the better 3D model (I have it).
For the FSD version there are many excellent repaints.
I must say, I think it is a very nice move of JF to offer demo versions of their products. I like the "buy it if you like it" concept.
Cheers,
Mark