Just my personal biased perspective: You are correct, there is no good definition of "Data Science". Just as any other buzzword, it is widely devoid of meaning

Just my personal biased perspective: You are correct, there is no good definition of "Data Science". Just as any other buzzword, it is widely devoid of meaning but useful to convey a general idea to certain audiences. Regarding R vs. Python, I personally use Python to process my data up to the point where I can hand it over to R in a convenient df-esque shape and use R for stats and plotting. Even if I do not require R for stats, I still use ggplot2 for plotting, though I'd be happy to see Seaborn or Bokeh evolve to a point where they can rival it.