12V vs 24V for your van build: which voltage actually makes sense?

I've done both. My Sprinter build is 12V with 300Ah LiFePO4 and a 2000W inverter — works great for normal vanlife. The cable run to the inverter is heavy (50mm², about 1.5m each side) but manageable. On a box truck conversion I helped with last year, we went 24V because the owner wanted a 3000W inverter for an induction cooktop and a small AC unit. In 12V that would've meant 278A continuous — you'd need 70mm² cables and a 350A fuse. In 24V it was 139A, much more reasonable with 35mm² cable. The tradeoff was needing a Victron Orion 24|12-20 step-down for the Dometic CFX fridge, the MaxxFan, and all the LED strips. Added about $250 and another point of failure. For vans under 25 feet, I'd say 12V every time unless you have a specific high-power need.