I currently own the Eagle Optics Ranger Binocular,"Platinum Class", as it was called at the time I purchased it. I use it, principally, for general nature observation. At home it's mostly birds, but on day hikes in Big Bend NP it could just as easily be cactus, lizards, or whatever else that piques the interest. The only area where the performance comes a little short is in lower light. To that end, I've been thinking about upgrading.
My initial thought was to go to an upper-end 10x42, but I've also begun to think about an upper-end 8x32. Given that they have the same exit pupil, and assuming we're comparing apples to apples (Leica Ultravid HD for example), is there an advantage to the 10x in terms of low light performance?
Your assessment of the situation is spot-on in regards to exit pupil and brightness.
The only advantage of the 10x would be that added magnification, no low light edge at all. While the 10x has the magnification advantage, you'll find the 8x32 to have a wider field of view, steadier for holding with one hand (lower power), and lighter weight.
Personally, I think a high-end 8x32 is about the best type of binocular for general nature observation that one can get.
If you have any other questions, just let me know.