I always prefer to keep my images in my library in vector form, so that they can be easily modified or scaled later if needed. However, when I am actually using these pictures in a LaTeX documented, a question arises if there is any need for vector graphics, when they can be replaced by high-resolution lossless raster pictures several times smaller in size? For instance, compare this vector picture saved in .pdf format (147 Kb) with the same high-resolution (1498 x 1498) losslessly compressed .png picture (8.31 Kb):
As you see, the difference in picture sizes is nearly 10 times. And the image is pretty simple.
I believe you will not see the difference in the printed document, and you will never really scale the computer version to the point when you see separate pixels.
So is there a point in using larger vector graphics instead of compact raster pictures in LaTeX documents? I don't talk about cases, when vector graphics actually occupies less space than raster (is it so often, by the way?).
P.S. When reading professionally prepared scientific articles, one often encounters vector pictures. If articles get bigger this way, why would the professionals use them?