I was asked about base64 vs a sprite image in CSS

Jake Archibald:

With base64 the image data is in the css file, meaning it gets downloaded even if it isn’t needed. Eg, if you’re using media queries to optimise image usage for mobile, base64 doesn’t help.

Jake Archibald makes some good points against Data URIs.

Data URIs make CSS sprites obsolete

Nicholas C. Zakas:

CSS sprites were a solution to the problem of multiple HTTP requests to download multiple images. Data URIs allow you to embed images directly into your CSS files, solving the same problem in a much more elegant and maintainable way.

I hate working with sprites, but I do it because it is or should I say, was, the best way to increase the loading speed of images.
Since a few minutes ago I never heard of Data URIs, but it is great and I think I will try it out very soon. You should, too.