I would have thought 50 mm objectives will always outdo 42s, but on a recent xmas birdcount I tried another birder’s 8x42 Swaros (I don’t know what model) while they tried out my 10x50 B6 Mavens.
The Swaros were brighter. We both noticed this.
I love my 10x50 B6s, but now I’m all like, hmmmmmm.
I won’t buy Swaro or Zeiss but I would (eventually, if I could ever afford them) buy 10x42 Noctovids if they too were brighter than my Mavens. I am lucky (or unlucky? : ) to have a Leica store in my area, so maybe one day I’ll test drive Noctos. I wish they came in 10x50s.
I went there once and tried 10x50 Ultravids. I was not moved by the view but I should try them again, too.