I have heard 8x are brighter and better........and probably are but I just tested some recently that were different !
I was hunting up in Canada recently and we were glassing big fields a lot and checking different hunting spots. 2 guys had Leica Geovid 10x42, 1 guy had Leica Geo. 8x42, and I had Leica Ultravid BR 10x42 .
We compared mine to the 8x42 several times and mine were better in low light than his 8x42. I personally could not tell any difference in FOV either. Anyway........for those particular bino's...........made me glad I went with the 10x42 because I fought with that decision a lot !!
Did not compare mine to the other 10x42's but probably should have ..........just for the heck of it !!