What size NOCO Genius charger do I need?

Specialist community consensus on r/batteries is that the GENIUS1 is best for maintenance only (it would take days to fully charge a flat car battery), the GENIUS5 hits the sweet spot for a typical car battery (around 12 hours from low to full), and the GENIUS10 makes sense if you're charging larger truck, RV, or deep-cycle batteries where you actually need the extra amps.