Couldn't resist trying to go further. We can use an implicit viewBox.
$ echo '<svg xmlns="http://www.w3.org/2000/svg" height="256" width="256"><circle r="1000" fill="#aad3df"/></svg>' | brotli -9 - | wc -c
83
r="1000" hits brotlis built-in dictionary, but if you target zlib then
r="2566" is better.
