I can tell you my experience as a js package dev, last tried a few weeks ago. We're building an npm package that's supposed to run on both node.js, deno & bun & the web.

This is an annoying to do for exactly two platforms: node.js, and deno.

node.js bcs it requires a workaround whenever something networking comes in: fetch doesn't work the same. So you structure you're code around having a node.js workaround. Same story for some other APIs. But you can test if itn works!

Deno is more annoying, you just can't test your package with deno before publishing. Before we released to npm, we installed a tar file and sent those around for testing. Works in node, in vite (node, for browser), works in bun, like a charm. Doesn't work with deno unless you switch to package.json, and you use exactly the subset of the spec that deno supports. You can't "deno install xyz.tar", you have to use npm for that (inserts a single line into package.json), THEN you can use deno to execute. No docs, no hint, just trial & error.

Even more annoyingly, npm & bun both offer 'link': in package repo, call npm/bun link, in the test repo do npm/bun link @yourpackage, and that's it, it's installed. Creates a dyn link to the source's build dir so you can rebuild without packing or sending tars or anything like that, you just build in your package dir and the test project is immediately updated.

Deno doesn't have that. What's worse, they don't tell you they don't have that. Also basically no error messages. It just fails in weird ways. Spent hours trying to do it. Now I just publish without testing for deno and wait for bug reports.

So out of the three: bun just works. That's it. Better than any platform. It just works, and it has a nicer CLI & nicer error messages, and it's faster on startup. It has the web api and the node api (i think) and its own api that's very nice as well, nicer than e.g. node. And e.g. if you run bun link, it tells you exactly what happened: this is what just happened, this is what you have to do to use it elsewhere. Node doesn't have that!

I think deno recognized bun's strategy of using npm dev's backbone as being the better call - that's why they're now slowly introducing node.js features, even though that goes against their original USP.