This is how simple it is to convert a C mount device to use prime focus. You unscrew the objective lens, screw on a 1.25" eyepiece barrel, put on the filter of your choice, and stick it into the focuser. The 1.25" nose piece costs about $20
This is a C mount device configured to use a zoom lens. This particular lens is a Vivitar 70mm to 210mm f/4.5 lens. I paid about $30 for the adapter and less than that for the lens.. Once again, to use the lens, the objective is unscrewed from the C mount device, and the lens with adapters is screwed on. This lens gives from about 2.7x to about 8x. This is a great range for locating bright clusters or small nebula an then zooming in on then for closer study.
There is this persistent talk that C mount is more complex but having used both, I would say that in use, if multiple telescopes are going to be used, C Mount is actually easier to use, especially because it is easier to use filter wheel with prime focus. Now one can't get as many magnifications as with afocal, but one will find that a great deal of obseving can be done with just prime focus and a barlow, and it is very simple to go back and forth.
I don't think buying a PVS-14 is a mistake, but to be put off by what people say is the "complexity" of C mount is also a mistake. In use, the C mount is often less complex to use, an some of the added adapters and things are related to the fact that you can do things with the C mount than you can't do with afocal.
Both will work well for astronomy, but the PVS-14 is not always as simple as it is presented to be, and the C mount is simpler than most non-users realize.
I recommend the Mod 3 because you can still do afocal if you want, but the configuration options are far greater with the C mount interface.
But again, both work well, it is just that one has more limits in what it can do. C mount has far more configuration options and in most of those, it can work with a 1.25" filter and in SCTs and refractors, it is pretty easy to go back and forth.. You can't move your filter slide from the inside of a Newtonian and move it to your refractor. Again, the talk makes it sound like the C mount is more complicated, but afocal has its own complications.
I have no vested interest in selling one solution over the other. I don't work for any of these companies.
I have used both afocal and prime focus (because I can even though I have a C mount device) and both have their pros and cons, and neither has a great simplicity advantage. The C mount just has more flexibility and in my opinion, is generally less to fuss with, though I am a major believer in filter wheels and C mount is more conducive to filter wheel use.
(New people might not realize that using a 70mm to 210mm zoom is the same range as going 50x in a telescope to 150x in a telescope. Imaging the difference that makes on the Orion nebula when using a telescope and apply that to viewing the Andromeda Galaxy in a hand held scope.. The difference between 3x and 8x is often a huge difference when it comes to large nebula or Milky Way structural detail.. Most people using C mount will tell interested people that they use their SLR lenses far more than they would have realized before they entered into image intensified astronomy. Low power observing with an image intensifier is a whole new experience.)
Both work though, and no one is going to miss anything that that the other can see whether they go afocal or C mount (which once again, can do afocal as well as prime).
While I personally recommend C mount, Afocal will have people that feel as strongly about it, so there is no right or wrong, but in applications there are important differences and I urge the perspective buyer to study both solutions before buying.