Gnuplot can handle data files with millions of points, that some users have reported to cause Matplotlib to crash. It's actually easy to make the plots look good. It can be controlled through a socket interface from any programming language, and seemlessly integrates with LaTeX.
We're about to start rolling out chapters from my book, which covers the latest version:
Hmmm, I've never had mpl crash and we routinely plot data sets with 10s of millions of points. We do a mixture of 2D scatter plots. 1D/2D histograms, and a few 3D plots. What type of plots are you generating? What type of data?
I never had the problem myself, but have seen a handful of user reports in mailing lists and SO. Perhaps recent releases are better performing. I used to use mpl regularly and found it very capable, but never liked the API.
We're about to start rolling out chapters from my book, which covers the latest version:
https://alogus.com/publishing/gnuplot5/
EDITed to reflect comment below.