Portable and open source is definitely good properties to ensure long therm thrust. If the standard has several implementations, it helps to ensure that the standard is concistent and usable in different settings, and discourages incompatible changes. It is also a good sign of popularity. I have not looked at HDF5, but I suspect there are many settings where a zipped directory of csv files are easier to use, as well as cases where the opposite is true. As we don't bundle the library with Julia, installation is an additional issue.
This is anyway only relevant for a long therm STORAGE format. That is a different requirement from a file to transfer data between machines, or work sessions on different days.
