This info is from another forum and has been my go to for information. I think he also has the same handle on rokslide but this dude knows his stuff.
The CL (Companion) line: This is Swarovski's entry level line. The components are quality BAK4 glass, fully multicoated lens surfaces, and a compact composite body. I have seen these binoculars and think they are really nice ergonomically, but they have a limited field of view, and show noticeable levels of pincushion distortion and chromatic abberration.
The SLC neu line is being phased out. This is the workhorse line from Swarovski. Glass is high-grade BAK4 with Swarovski's excellent trademarked coatings (Swarodur, Swarotop, Swaroclean). Most of the models in this line are very well optimized. They are known for wide sweets spots, deep depth of field, low distortion, and good aberration control.
The EL line was a game-changer in optic design. The EL was the first open bridge binocular design, and left other makers scrambling to copy it. The technology in the ELs is the same as the SLC neu, using the same grades of glass and coatings. The optical designs are a little different, and the images end up a little different as well.
To answer the PM I had that started this post, the differences between the EL and SLC neu are mostly in build design (open bridge vs. piano hinge) Allbinos.com rates the SLC neu 10X42 optically higher than the 10X42 EL in their testing, but it does not take into account the ergonomics of the open bridge. Personally, I think the images are extraordinarily similar, with the EL showing a little more pincushion distortion, field curvature, and edge CA. Both provide world class images.
Now Swarovski has upped the ante with their latest super-performing, super-expensive binoculars. I believe the primary reason they have gone to such lengths and expense is from competition from lower priced binoculars. In any case, the newest Swarovski bins perform at a very high level.
The SLC-HD series is similar in design to the SLC neu, but incorporates flourite glass in the objective. This reduces CA. Allbinos.com seemed to find CA in their test sample, but I have looked at the SLC-HD every chance I have gotten. I don't see it, and I am pretty sensitive to CA. The SLC-HD provides the finest binocular view in the world in my opinion. It has just enough pincushion distortion to avoid the rolling ball effect. IT has little to no field curvature. The result is super high levels of apparent resolution. It is a very impressive instrument. The single birdge design is also very comfortable to me.
The EL Swarovision series is a large, long double bridge design with every bell and whistle. The image in the Swarovision is just like the SLC-HD, except extremely flat. There is no discernable field curvature or distortion, to my eye. I can't see any CA at all. The stable image is just about perfect. The only issue with the Swarovision is the lack of distortion. It is so flat, that the rolling ball is quite pronounced to me when panning. Perhaps with time I owuld become accustomed to it. But, I don't know why I would try it, when the SLC-HD has the same image, with just enough "bend" to ease the rolling ball.
