Riven, what kind of terrain do you expect to use them in?
Forgive me if I'm about to say stuff you already know.
Personally, I just don't get the point of 8x bins. Yeah, I know they give you a wider filed of view but I'm not convinced (based on personal experience) they really give you the zoom to make a good identification of really 'see' the details of the animal. Watching the birds on the feeders in the back garden? Yeah, sure. But as a decent wildlife spotter, given the ranges you will mostly be at? No. Most birdwatchers use them as a quick ID tool so they can get the scope on it for a much better view.
In the woods? Yeah, OK, an 8x optic is probably all you need because the things you will be looking at will be closer (though a large objective lens is what you'll need to get a better image in lower light conditions - the 42mm you are looking at will be fine).
But what if you are in open terrain - the coast, or an open field, etc? You may be looking at stuff from quite a distance. An 8x will not be up to it. Instead of a small brown dot what you'll see is a slightly larger brown dot.
A 12x is what you'll need there.
So what I would recommend is splitting the difference. If a one-size-fits-all set of bins is what you are looking for (assuming such a thing exists) then I'd go for a 10x42.
The 10x will still give you a wide enough field that you can find what you are looking for but also give you a slightly better reach at range. The 42mm lens will let in enough light in darker conditions.
Here's the rub I've always had with a 42mm lens - it's too big and heavy to have in a belt pouch which means you'll have to keep it around your neck. At which point, why not just have a 50mm lens anyway?
That's why, personally, I have two set of bins - a 10x26mm lens for carrying on the belt for 'opportunity spots' when out for a walk and a 12x50mm lens when going out purposefully to spot stuff. Actually, I have a 10x42mm lens as well but never use it because...well, because as I said above.
Again, apologies if you've had bins before and are happy with an 8x, I just want to save you some money before you spent a lot of cash. As said before, have a try of some before buying - and have a look at some 10x bins as well, even if it's just to discount them. Me? I find 8x very disappointing because they promise you a good view but never really get quite close enough.