Jez, check that the browser has hardware support turned on (or if it even exists)
Actually, there's more - a lot more.
In my day job, we develop browser based systems. A number of performance issues can exist at the client level outside of the base capability of the browser, especially regarding rendering capabilities which include:
AV interference (script analysis, heuristics)
Hardware support / enablement
Performance toggles
virtualization issues
browser "plugins"
proxy controls
and many more.
Chrome should beat edge on a lot of things and build numbers are important. What chrome version for instance?
TBH, if you are making product for the browser market, then you can't make any assumptions.
First, you need to make a benchmark app which you can use to work out if something is working unexpectedly (e.g. a specific set of functions which target different elements (number crunching, GPU throughput etc.))
Second, you MUST code variation control into your apps - a kind of "check my environment" thing which assesses the user's potential experience and reports anticipated problems such as low FPS
