If you tripod mount an 8x you'll be more effective than hand holding a 10x. Something to think about
I used a similar thought process to pick the 12s over the 10s. Same FOV as my previous 10x42 ELs and better magnification.I did this same exercise this spring. I went to the store fully intending to buy the 8s. I looked through both for quite some time at dusk and ended up walking away with 10s. The 8s were phenomenal, but the field of view is so wide with all of the NLs that I felt the 10s have most of the advantages of "regular" 8s, but were still 10s (if that makes any sense). I don't think you can go wrong. I think this is the definition of a "first world problem."