Having tested both side by side recently, I'd say the Conquest HD punches way above its price and is pretty close to the EL (Swarovision) in terms of sharpness and brightness.
I'd say the EL (mine is a 2014 SV that was repaired by Swarovski last year and got a new focus) delivers an image that appears brighter, but I'm not sure if the % of light that goes through the objective of the EL and Conquest is actually very different (when it comes to the 10x42, Allbinos has measured actually 93 % for the Zeiss and 91 % for the EL), but the way the EL delivers the image makes it appear brighter, it's difficult to put it into words. The Conquest appears a bit darker, but maybe because it shows more contrast (like in more black areas), which is something I've seen when comparing the EL to other binoculars. And this is probably one of the strengths of the EL, because this perceived brightness allows for an astonishing level of detail, it somehow pulls more information (tiny, minute details from feathers, leaves or whatever you're looking at). This is by no means a demerit of the Zeiss, which if you compare them directly A-B, offers a very similar level of sharpness. Let's say that they offer different approaches to being very sharp and bright. I'm not sure if the flat field, and the fact that the image is sharp to the edge on the EL helps creating this perception of enhanced sharpness and transparency. I really don't care about flat fields (except for astronomy) but I love the image on the EL, so maybe the field flatteners have side effect of giving a more pronounced feeling of "being there", since basically the entire image is "sweet spot".
As for colour representation, the colour on the Zeiss appeared a little warmer (somewhere where yellow and green meet) after looking through the EL, which I found surprising, because some years ago I had the 8x42 Conquest HD and I remember a cooler hue. Compared to the Conquest HD, the colours on the EL seem to lack any tendency towards a particular colour.
Build quality (or the perception of ruggedness) is very high on both, but it's again expressed in different ways. The Conquest HD seem to be built like a Panzer, but they're less refined. The eyecups are nowhere as nice as the EL, and the general feeling when holding them is that they're a tool for the job (which is really something nice, since tools from different activities are usually things to love, be it a knife or the peel of a baker), while the EL are nicer to hold in the hands and have a much higher feeling of luxury and attention to detail. But, again, this is no demerit of the Zeiss, I could see how someone would actually prefer the look and feel of the Zeiss and despise the colour and appearance of the Swarovski (the fact that it spots a huge logo with the name of the company in capital letters doesn't actually help with my idea of understatement; luckily the Field Pro got rid of it).
So, if you look at the retail price (around 800 € for the Zeiss and 1600 € for the EL, although both can be found for less) I'd say there is no way the EL can justify costing actually twice the price of the Conquest HD. I'd say the image of the Zeiss goes "beyond 1000 €" and could satisfy you 100 % in every single way. Actually, the reasons I keep an EL and not the Conquest HD don't have to do with the image (I'd be completely happy with the Conquest HD), but have to do with handling/using. The Conquest has 3 things I don't like that much, or (to put it other way) the EL does better for my taste:
- The Conquest HD feels bulkier, which for a compact like 8x32 is a minus on my book, although people with large hands might actually find this is a plus.
- The eye position on the Conquest HD is more critical. Again, not a demerit of the Zeiss, but this is just the area where the EL excels for me: it behaves almost like a 8x42, it's so easy to find the right position, while the Conquest HD is more prone to "kidney-beans" (having black crescents on the edges of the images).
- Last but no least, the Conquest HD is heavier than the EL. 630 vs 580 g. Yes, it might not seem much, but there's less weight difference between the Leica Ultravid and the EL than between the EL and the Conquest HD. It's probably not only the weight, but also the fact that the Conquest HD is shorter but bulkier (with thicker tubes) that makes it feel heavier. Again, something some people might not find relevant.
But, on the other hand:
- The Zeiss offers a better performance in extreme light situations (suffers from less veiling).
- The focus on the Zeiss is faster, really superb, many people would find it can be even better suited for birding (nothing wrong with the one on my EL, is smooth as anything, actually better than my partners EL - FP)
- The Zeiss is cheaper, I wouldn't call it a "bargain", but I'd say if you can find it for around 700 € new or 500 € used is close to the best possible value.
And, to end with things that are hard to understand... while both Zeiss and Swarovski boast amazing customer and repair service (I've used them both several times and I just can't praise them enough) it's hard to understand how the Conquest HD can be sold with the lousiest objective covers ever to be created by man, and the EL Swarovision comes with the most over-engineered and at the same time useless rain guard
Imagewise, I don't think there's a way you can find a 2x price difference (if actually any difference), in fact, some people might actually prefer the non-flat image of the Zeiss.
Shape/grip/feel do show the Swarovski is a more expensive device from an upper category.
You simply can't go wrong with the Zeiss. I'd only go for the Swaro if you had eye positioning problems or find the Zeiss too heavy bulky.
I hope that helps.