Neither one, the B.6 is what you want. Specifically the 10x50. You get all the good from the B.2 9x45 (5mm exit pupil, great field of view, exceptional optics) in a better (ie smaller) package. The b1.2 10x42 is an ok bino, but they pale in comparison to the b.2 and b.6. The physics of a 10x42 won’t allow them to perform in low/poor light like the 9x45 and 10x50 will. There’s a reason the b1 and 1.2 aren’t ever mentioned in a comparison of “maven vs swaro/Leica/zeiss,” it’s always the b.2 and lately, the b.6
If you get the b.6, do the 10x50. Easier to handhold than a 12x50 and you get better low light performance
If you do the b.2, do the 9x45 for the same reason.
Don’t buy the b1.2, it won’t keep up with the other two in suboptimal conditions (small exit pupil and low twilight factor).
EDIT TO ADD: this conversation changes a bit if you want an 8x, but I won’t opine there, as I personally think an 8x bino is a waste of weight and space and money (for how I’ve always hunted). So my post is admittedly biased because I’ll never buy anything below a 10 (another reason I say b6 over b2), no matter what anybody says or what a marketing campaign tries to sell me on haha.