The weight advantage in real use
At 18.8 oz, the Viper HD is one of the lighter full-size 10x42 binoculars on the market. That 7-oz gap over the Maven B1.2 is roughly the weight of a full Nalgene bottle cap — not trivial when it's hanging around your neck for eight hours. For thru-hikers or anyone counting ounces, this matters. For a weekend birder doing a slow walk from a parking lot, it matters less.
The VIP warranty isn't just marketing copy. That unconditional coverage adds real value to the purchase, especially for gear that goes into rough field conditions.
Optical quality: good but not quite elite
Vortex calls their glass "HD" but it's not the same as true ED (extra-low dispersion) glass like the Maven uses. In practice, center sharpness is excellent and color rendering is good. Where you notice the difference is at the edges of the image circle — looking at a bird near the edge of the frame, the Viper HD softens more than the Maven B1.2. For most users this won't matter. For dedicated birders who are often watching subjects at the perimeter of the field of view, the Maven's edge performance is worth the premium.