I've been using parcel because it's the only thing I know and I always thought it was slow but it claims to be fast and I'm new to js so I took it's word for it. According to this it's the slowest of the lot, though. Why does it claim to be "blazing fast"?
Yes this was a surprise for me too. The benchmark I used for esbuild deliberately tests full build time without a cache, since that is an important metric to me. I assume Parcel is talking about incremental build times when the cache has already been populated. In that case I'm sure Parcel is not as slow.
Depends on what you are measuring. If 95% of what you care for is development mode, then it may not even be faster. Individual files only have to be compiled once in watch mode. For some bundlers even between builds.
If you measure production builds, it's a different story. As every change has to most likely redo tree shaking and minifying over all the code. If you want source maps, it gets even worse.
For my project with maybe 30 dependencies in package.json, the incremental build finishes within a second on watch mode when I edit a file, so it's quite fast in that case.