I was in the same boat a few weeks ago. Honestly, for your use case (browsing, writing, light photo editing), the M2 is probably the sweet spot. The M3 is faster, sure, but you likely won't notice a huge difference in everyday tasks.
Battery life is pretty comparable between the two. Both are excellent. The M3 might have a slight edge, but we're talking minutes, not hours.
The M3 does have faster Wi-Fi (Wi-Fi 6E), if that matters to you. If you have a Wi-Fi 6E router, you might see a speed boost. Also, the M3 supports two external displays (with the laptop closed), which the M2 doesn't. But if you only need one external display, it's a non-issue.
I ended up going with the M2 because I found a great deal on a refurbished one. Saved a bunch of money and it does everything I need it to do. If the price difference is significant, I'd lean towards the M2. If the prices are close, then maybe the M3 is worth considering for the extra features and slight performance bump. But for your workload, I wouldn't stress too much about it!