I think Luke was comparing the exit pupils of the 12X50 and 10X32, Larry, and so should have an exit pupil/apparent brightness advantage.
BB, you are right. I just wanted to point out that just because the objective lense is bigger doesn't mean that the image will be brighter. For example, if the Zeiss Victories were 7x32s instead of 10x32s they would have been "brighter" than the 12x50s.
All things being equal, yes, and there is also the ability of the binocular to transmit light to take into account. Bitterroot clarified this above - the number of lenses, type of lenses, and I will add coatings affect light transmission.
In other words an 8x32 porro prism with 98% light transmission will be brighter than a 7x32 roof prism with 91% light transmission, and potentially some 8x42s that have fallen behind.
I have not seen this statistic published by many binocular manufacturers, so we have to dig for it. It would be like publishing horse power and not miles per gallon for a car manufacturer.