I'm jealous. I made a decision a while back to upgrade and extend my optics as I prepare for retirement in a year or so. I am about to turn 70. I spend most of my life relying on and enjoying an 8x32 Nikon Premier. I still have that binocular. I knew nothing about Swarovski at the time, except by reputation. As I started looking around for my first purchase I realized that the NL was a thing that had burst upon the market. I got adivce to stick with 8x. I knew I wanted 42. So, I ended up up with 8x42 NL, and I love them. But ... a higher power bino is also calling out to me. I scratched that higher power itch first by picking up a good scope. I do like having the scope. It is a great tool. But, 12x binos continue to call out to me. Seems pretty obvious where this is going to end up.
My internal debate now is whether to go with 10x with the plan to sell the 8x, or go 12x and plan to keep the 8x. I'm not tempted by 32s. I am going to stick with 42s. I find the 42s are fine for me as far as weight and compactness.
I doubt that you will see enough difference by only going up to 10x from your 8x. It might not be worth it in order to sell the 8x. Since I now have the 12x, it will probably get used a lot more than the 8x for back yard bird viewing. The detail you can see at that power is close to breath taking. Having less FOV view seems insignificant at relatively close distances. Moreover, in brighter light, depth of field is still pretty good with 12x. However, in darker woods where you need more depth of field, or for viewing distant landscapes and for viewing sporting events, where you might appreciate more FOV, the 8x might be preferable. Having both, if you can afford it, allows you to choose the best tool for what you want to do, on any particular outing.
On the other hand, If you can only afford one pair, the 10x, might be the way to go. Or, if you only want to pack one pair to be used in multiple different situatiions (close and far, or bright and dark), the 10x might be the GoldieLocks pair to carry, even though, you might be giving up some on the magification when compared to the 12x, or FOV when compared to the 8x.
What has been, for me, surprisingly taken out of the decision making process, is ease of handling differences. Because of their fantastic ergonomics and balance, all magnificaton versions seem easy to hold steady without fatigue, even when not using the optional head rest. Also surprising to me is that I see no difference in brightness or in eye placement ease with the 8x or 12xNl, in spite of their different EPs. I guess you can't go wrong with any of them.