I disagree. I have had all those binocular's and compared them in low light and the Conquest and SLC are definitely the brightest in low light. IMO the Conquest is the brightest in low light of the four. Zeiss tend to have very high transmission in general and I can see it. You get over a 4% difference in transmission and it is obvious. The SLC though has better contrast than the Conquest. One weaker area of the Conquest HD is contrast. For example, the Swarovski CL 8x30 has better contrast than the Conquest HD and that is one reason I prefer the CL over the Conquest.
The Conquests are brighter because they were engineered to allow more blue light through which dramatically increases our sense of brightness. TV manufacturers do this with their tvs on display in stores by upping the blue so that they appear brighter. But what this does, is effectively lower the other colors intensities. Reds, Yellows, and oranges are especially affected and will appear much less vibrant and in my opinion, slightly dead. Birding is about enjoying nature and the Conquests make everything look slightly less beautiful in my opinion. I am probably in the minority on this, I was trained as a painter and i put a ton of emphasis on color, probably way more than other people care about, so keep that in mind.
The Conquests are extremely sharp though.
I eventually ended up with the SLC which I LOVE!! It does not have the absolute best color I have seen, but the colors are very neutral and vibrant. I can't remember which one, but one of the Leicas had the best color yet that I have seen but it wasn't very ergonomically comfortable.
The SLC is so easy on the eyes and super relaxing. The armor is also very comfortable and super durable. I have had n=mine for a few years now and show absolutely no wear at all. My conquests have not held up as well and show much more wear than the SLC's even though they have only been used a 10th of the time. They are starting to get a powdery white surface. Not sure what that is about.
I have tried the HG's at Cabelas a few times and was not impressed with them. They did not wow me like others do.
I would highly suggest the SLC. My wife has the 10x50 Swarovisions and I even prefer the view from my SLC's to them.
Be aware that they have very slow focus so they are frustrating to use during warbler season, which is only a month or so. But other than that they are amazing.
You won't regret it and they will last your lifetime.