The M3 is slightly better, but you probably won't notice day-to-day.

You’re looking at maybe an extra 30-60 minutes of battery life on the M3 under a typical office workload — spreadsheets, email, video calls, text editing. Apple rates both at 15 hours wireless web, and in real-world testing that holds up.

The M3’s efficiency core is a bit faster and uses less power than the M2’s for light tasks. So if you’re mostly in Safari and Slack, the M3 will sip power more gracefully. But if you plug in at lunch or dock at your desk, the difference is academic.

If battery life is your absolute priority and you never want to think about charging, the M3 wins. If you already have an M2, don’t upgrade for this. If you’re buying new, get the M3 because it’s the current chip — not because the battery changes your life.

The real battery killer in either one is display brightness, not the CPU.