The USB rechargeable lights are much more convenient to charge, and as others point out, they work much better. I'm not happy that I usually have to replace the entire light when the battery dies, but this is a price for so-called progress.

I have a fantasy of installing an electrical system on my bike, powered by an external 5V lithium-ion battery, but it will take some work. I could power rechargeable lights, including those whose internal batteries have failed. I could also power *some* models of lights intended for dynamo use. If I ever succeed, I'll post here. My spouse has a habit of carrying one of those batteries when she goes out, and she charges her phone with it. She could extend that habit to the bike. She cannot, however, remember to keep her bike lights charged, so this would be an improvement for her.