usually a 1mm larger exit pupil wins against more transmission, so the Ultravid 7x42 should be a tad brighter than the Swarovski 8.5x42 in the twilight.
I don't know why the Swarovski's are generally said to have such poor stray light suppression, that EL 8x32 may be susceptible here...
there is no reason why bright binoculars shouldn't have good contrast too!
The best example here would be the Swarovski SLC 8x56.
All manufacturers have a different color philosophy, the Zeiss love green / yellow, Leica red / brown, Swarovski EL blue / white, the SLC very neutral...