hMonkey
Advantages I see wrangle vs text file on disk:
Selfcontained. I cannot be lost that easily. If it exist in the scene is much easier to find by other artist.
How is the going to get lost anymore than a .hip file can get 'lost'?
It's sitting in a Houdini 'ecosystem' under $HIP. I personally back up the directory that holds the .hip file.
Because it not only has my functions but also other subcatagory folders like geo and others.
The artist is actually going to have an easier and quicker time finding the functions if they always look to vex/include,
rather than possibly having to hunt through a network to find that one 'original' source node that has the function being
referenced.
hMonkey
Easy to have multiple version. Its easy to test diferent versions by simply duplicating the wrangles.
It's easy to make and test multiple named versions as well with an external referenced file by simply copying and pasting
within the same file or new file with different name. If you're only at development stage then you can put your function code
directly in the wrangle, since like you say you're only at development stage. So as it is Houdini already has the 'feature' you
are looking for.
hMonkey
Can use presets which hopefully get even more functional in future versions.
Externally referencing you vex functions does not preclude you from not being able to use presets.
hMonkey
Can easily shared with hdas.
Vex functions can already be defined and used within an hda.
hMonkey
Using relative paths inside node networks can easily duplicate both the definition wrangle and the wrangles calling the functions. This way would make the dependencies a bit more flexible.
How is this any different that ones reference to a file vs. another wrangle? A wrangle can be duplicated with the same code that references the function externaly and is just as flexible.