tl;dr: xz compresses better but is significantly slower. This isn't the deepest analysis of potential tradeoffs you might be able to find.
A few reasons why gzip is still useful to have around:
* Speed is critical for many applications, and so size can take a backseat when performance is critical or resources are low.
* gzip is basically guaranteed to be available everywhere in utility and library forms.
* Download speeds vary and so the faster your pipe, the less the archive size factor will matter, and the faster-worse compression might win out in other comparisons.
* xz doesn't compress every type of data this much better than gzip. I've dealt with scenarios where the difference is consistently less than 2%, and the extra time xz spends is actually a tremendous waste.
Sure, for package downloads where xz files will be significantly smaller it makes sense to save the bandwidth, time and storage space. But it's not 100% cut and dry.
A few reasons why gzip is still useful to have around:
* Speed is critical for many applications, and so size can take a backseat when performance is critical or resources are low.
* gzip is basically guaranteed to be available everywhere in utility and library forms.
* Download speeds vary and so the faster your pipe, the less the archive size factor will matter, and the faster-worse compression might win out in other comparisons.
* xz doesn't compress every type of data this much better than gzip. I've dealt with scenarios where the difference is consistently less than 2%, and the extra time xz spends is actually a tremendous waste.
Sure, for package downloads where xz files will be significantly smaller it makes sense to save the bandwidth, time and storage space. But it's not 100% cut and dry.