True due to the larger lens diameter in the vultures, but location (where you are using them) will come into play.The vultures will be much brighter and if you do a side by side comparison you will find the image's a bit sharper and crisper. Also the vultures do not come in 8x42. 8.5x50 would be the closest to compare.
I think the glass is identical. The less light you have, the more important the amount of light the optics gather is. The low light conditions are extrmely important for most if not all of us. If the optics gather more light and the glass is comparable the sharper the images will appear.True due to the larger lens diameter in the vultures, but location (where you are using them) will come into play.
The larger diameter isn't going to come into play as much in the woods where light coming in is blocked as it would in an open field.