As the main developer of humdrumR, I can address Ben's question from my perspective, but this is sort of addressed at the whole group. I think the ideal relationship between humdrum and humdrumR has yet to be really worked out.
We are still working out for ourselves whether, pedagogically, it makes sense for users to first learn the original humdrum toolkit (and humdrum extras) before learning humdrumR. In some ways it makes sense to do so, and humdrumR actually emulates the original toolkit in many ways, so it can work. However, not a lot of people are interested in learning (or installing) bash/awk based tools at all; Learning R/RStudio is more appealing, especially since you eventually need something like R (or Python) to do stats, plots, or more sophisticated analyses. It can feel (for students) like, "why are we learning these old-fashioned bash tools if we won't be able to do the full analysis with them anyway"? (I use bash all the time myself.)
Ultimately, I do envision that new humdrum users could indeed "skip" the classic humdrum tools and start with humdrumR. humdrumR can (or will eventually be able to) do everything the humdrum/extra toolkits can do, and it also enables a lot of things that they can't, including but not limited to statistics. That being said, the things that "classic"/extra tools can do, they can do faster and cleaner than humdrumR. For example, the mint command is amazing. You can do it in humdrumR, but the ease and speed of the original mint crazy.
Here is a scenario: If you want to find the most common scale degree in the soprano voice of the Bach chorales, you can do that faster and (slightly) more simply in the original humdrum toolkit, compared to humdrumR. But if you want to find the most common scale degree in each of the four voices, it will probably be just as easy to use humdrumR. And, if you want to find the most common scale degree used in each voice, but only in the upper half of each voice's vocal range and only for durations longer than an eighth note, it's going to be much easier to do that in humdrumR.
Of course, as Yuri pointed out, humdrumR is still in development, and still has bugs and features not yet developed/implemented/documented. I can tell you that I use bash a lot personally, just for day to day work, and of course I use humdrum data almost exclusively in my work, but I don't think I've even had the humdrum tools installed on my machine for years. I use humdrumR exclusively...though to be fair, I am the only person who entirely understands how it works.