Advantages:

• Smaller package size
• Simpler build code
• Maybe fix compatibility with some tools, like Switch from package type to resolve issues with bun #109

Disadvantages:

• Annoying for people on old versions of Node.js (although all current versions of Node.js now support require(ESM)
• Might introduce compatibility problems with some tools (especially Jest!)

That last point is the big one, since a lot of people use fake-indexeddb with Jest, and last I tried it was still really annoying to get ESM stuff working right in Jest. So this issue might sit unresolved for a while.