John,
I think you're going to receive questions about why those are your choices.
Usually people ask about a choice between two 8xs or two 10xs, but choosing between a full sized 10x and a midsized 8x is a mixed bag that suggests that you have varied needs that sometimes require extra magnification (such a shorebirds) and other times requires lower power, lighter, more compact bins (hiking, nature trails).
To quote from the canon of Ingraham Philosophy of Birding: In theory, an exceptional 32mm glass should show all of the detail the human eye is capable of seeing. In practice, and hand-held, 32mm glasses equal the performance of larger glasses in all but the most extreme conditions. When you factor in the ease of carrying and using the smaller glass, 32mm binoculars begin to make a lot of sense.
Ingraham's philosophy would suggest going for the 8x32 EL.
However, if your needs are such that you sometimes prefer a 10x bin and at others prefer a midsized 8x, why not "split the difference" and consider a Swaro 8.5x42 EL?
Hand held, you will get around the same resolution as the 10x42 Ultravid, if not better, due to less shakes, and you will gain a larger FOV, larger exit pupil, less CA (unless you meant to write Ultravid HD), and possibly better ergonomics, depending on your preferences.
With the new Swarovision EL out now, you will probably find some good buys on the previous model (check SWFA, Camerland, and eBay camera and optics Stores).
A better question to ask might be, which should I buy, an 8.5x42 EL or an 8x32 EL?