With gzip sizing is about the same, but processing speed wise it is not.
Same with csv data, for download size it really pays off to preprocess and pack into arrays of binary structs before compression.
This is part of a bigger class of effects in preprocessing data before compression, it is often surprisingly effective. For example delta coding or columnar format (SoA vs AoS) can yield big improvements depending on data.
With something that's grabbed once and cached likely forever I think the tiny bit of overhead for JSON won't make any difference. I've done this too and yes, of course a flatbuffer would be faster but the speed is just related to the initial download and caching. Beyond that you'd keep it in whatever structure is more efficient for the app to re-use.
Why would you pull in data from one format and keep it in the same format forever if it's not optimal for the device AND it doesn't need to be modified and sent back? Whenever I work on mobile apps and I have to cache data coming over as JSON or XML I store it where I can quickly re-access and NOT in its original format.
This thread seems like a conversation about how you can shoot yourself in the foot when it's very easy to avoid.
> I haven't heard of SVG renderers storing SVG XML files in a more efficient format.
Me neither. Sounds like it could be doable. Not sure how this related to our conversation though.