I’m decided as a pair for putting in my pocket for every time I step out, like the leatherman squirt I always have in my bag. Does the job but only as a convenience.
For serious birding (and pretty much anything animal related), I am dithering on buying some very good used EL 8.5, or waiting for a deal on the 10 NL. I know the former will be good enough, but the latter are better!
I’ve tried the NL 10x and they seem to have as good light gathering as the EL 8.5x
I realise that sounds counterintuitive, but that’s my experience.
At some stage I’ll probably replace my 25 year old Leica Trinovid 8x42s. If I do, i’m pretty sure it will be a contest between the NL Pure 10x42 or the Leica 10x42 Noctivid.
I was set on the 8.5 I tested as the really helpful rspb staff suggested it would be a better fit for my type of use: busy backgrounds, trees, and a fair bit of evening use.
That said, the Zeiss Victory SF 10 seemed on a par. I’ve read the NL are so good you can up a size and not notice on brightness. No stock of those to play with.
I figure that if I get the EL I’ll always hanker for the NL.
But then I have to ask if they are worth the extra for me, as I suspect my annual mileage is a lot less than yours!
So I’m not rushing. Any used NL and I think I’ll buckle!
I’ll take advantage bore you of your experience at Settle.
I appreciate the portability argument but top end bins are in another league whether that be the Zeiss, Swarovski or Leica.
Why are you telling me 
I don’t need convincing
Have you considered getting some decent bins Paul?
No, I’ll stick with my 25 yo Leicas for now.