Well here are some local data from a highschool in the Netherlands:
Approx 50% of our pupils use Chrome at home as default browser (on windows)
The rest is mainly Firefox (>=19) and MSIE (mostly version 9 and 10)
Because of MathML in WIMS our school switched from default browser Chrome to Firefox.Our ‘systems administration’ preferred Chrome because it’s light weight and very fast on older pc-systems.
In using MathJax our pupils (and sysadmin) can use their favorite browser and use mathml…and canvas…and svg…and html-inputfields in MathML 🙂
joke