I just posted a very detailed the observations Peter and I made this past weekend on the Deep Sky Observing forum so I would direct you to that forum for an in depth description of the wonderful M43.
I will say this as a repeat though. If this nebula were somewhere else in the sky besides being right next to M42, it might be a showcase object all to itself. It is like a Mini-lagoon nebula and the amount of detail we could see was quite considerable. What a remarkable view (and conditions were not at all great by the way. Just the power of the image intensifer working here and under really good conditions, I would think that it would be quite staggering).
Here though I am going to focus on the comparisons between the PVS 7 A/C, B/D, and the Mod 3.
Now clearly, the mod 3 starts at a great advantage because Peters tube is a really excellent L3 filmess tube with stellar signal to noise, high resolution, and good EBI.
But that is not the whole story.
I recently bought a PVS-7 A because I have read several times on the gospel of all things we call the internet that the optics of the PVS-7 A/C are a bit sharper than the optics of the B/D. The A appears to use a different collimator and optic arrangment but the most notable difference from the outside is that the eyepieces look like glass. Now I don't know if they are glass, but they look like glass and where the PVS-7 B/Ds I have owned have tended to show what looked like clear plastic lenses with little or no coating, the PVS 7 A has dark green coatings that look similar to many multicoated eyepeices. I don't know if they are glass and if the coatings are much better, but it gives a very convincing appearance of being better just looking at them and not looking though them.
We started with the L3 filmless tube and while it was tempting to move the scope to M42, the amount of detail in M43 sucked us in so all comparisons were done on this target.
And here is how it turned out. M43 is a fairly bright target so even at f/10, the nebula was fairly bright. The contrast of the nebula against the background was quite evident and the major channel with the sharp bend was easy.
So, how would the PVS-7s do. Well, pretty darn good! Now it was a very cold night for Austin with temps in the 30s, and this may have helped by lowering the EBI in my own PVS-7 which has a very high S/N, but a so-so EBI figure. Peter's PVS 7 appears to be quite excellent as well (and he got a great price on CL) and going back and forth I have to say that I could not really say the A was sharper in any easy to see way. The view in both was not that far off of the L3 tube with all of the higher medium and low medium contrast detail. The view in the L3 though was absolutely sharper and some of this was of course due to the optics and some to the tube.
But the PVS-7s did fairly well! Why? Well I suggested to Peter that he close one eye, study the scene, then open the other eye. He only had to do this once and he remarked to me that he could indeed see an improvement in detail when using both eyes. Now again, the view was not as crisp or as detailed as in the L3 device but the point here is that binocular summation does allow the PVS-7 to offset at least some of the limits of the tube performance. Had we not had an L3 fimless tube monocular there, I could have seen most of the same detail and been quite content because the view was far better than I have ever had using any telescope up to the C14 under similar sky conditions.
This is a fantastic object!
I was unable to do extensive side by side, and while the A/C may be a bit sharper, but if it is, it does not jump out at you.
As far as the other ways to compare, Peter immediately noticed the eye relief of the A/C. It is very generous at about 25mm and this makes it very nice to use in a telescope and I would think with glasses. But this generous eye relief comes with a negative. When hand holding, if you don't have eye guards on (the way an eyeglass wearer would) you get blackouts easier. The eye guards on the B/D kind of lock your eyes in position and you can view without any blackouds even hand holding heavy lenses. I find it harder to hold the picture in the A/C, but mine does not have eye guards and now I am thinking of putting some on.
The focus on the 7 A/C eyepieces is also much easier to access but the rubber textured ring does not have the feel of the outstanding castle profile of the B/D, which makes it possible to turn even with heavy gloves. The A is not difficult to turn but It is a little 'notchy' the way hard plastic threads can be (stick, slip) The B/D takes a lot of pressure, but once turning the big diameter makes small adjustments easier I think. For telescope use though I love the long eye relief of the A/C.
One thing I miss on the A/C is the ability to put an IR Illuminator spot device on it and the IR illuminator itself seems a bit weaker. The B/D has a raised post and the spot device just pushes in place and you can twist it to get a tight spot out to about 30-40 feet. For terrestial use, this is a very desirable feature to me and I do use my PVS-7 a lot for non-astronomy purposes so I miss the IR spot ability.
I kind of prefer the small on-ff, Pull-click switch on the B/D while the A/C has kind of a paddle with a button that has to be pressed to have IR on. The B/D has a monetary on and once again, I kind of like that option. A/C is either on or off and it is just quicker and easier to twist the knob into momentary on.
There are a few operational differences but it is hard to call out any as good/bad when one is compared to the other.
I won't be able to do anymore side by side testing because I sold one of my PVS-7s and the other is now an empty housing because I moved my best tube into it. It might be a little sharper but it is not easy to see this and I think a bigger reason to buy an A/C was if you needed the extra eye relief and the A/C is wins big here.
And I have to say this one more time.. If M43 were on the side of Orion from Flame and Horse-head, it would be a showcase object. It is that good! it is just so close to M42 that you can't hardly tear yourself away to study it.
But you should! Makes Trifid look sad and rivals Lagoon and Flame (at least I think) use 100x and do your very best to avoid the temptation to drift over to M42 and you will be richly rewarded.