Well, it depends what is slow with PGFPlots.jl (julia side or rendering side).
PGFPlots in general is not very fast so if your requirement is for the plotting backend itself to be fast, it might not be what you are looking for.
Not sure what you are referring to here — PyPlot has all of Matplotlib’s output abilities, which means you can output vector graphics (SVG, PDF, etcetera) and any resolution that you need.
I can’t reproduce with PyPlot.jl. Using figure(dpi=600) when plotting some random data, looks good to me, and savefig("foo.pdf") produces vector graphics that also look good.
This should not be surprising, since Matplotlib is extremely widely used and hence is pretty solid.
I have no idea about the Plots.jl interface to PyPlot, which I don’t use, but you could try to file an issue with a minimal working example.
This seems to be a specific issue with Plots.jl and not with the individual plotting packages. I use PyPlot on both 0.6 and 0.7/1.0 and have not seen that issue so far.