Axios vs Superagent
The difference is unlikely to be related to the raw speed of the client. Both use Node’s HTTP library or the browser’s built-in XMLHttpRequest. Most likely what you’ve observed are slight differences in timing related to event handling.
I’d base my decision on other factors, like which API you like better, and library size (for a browser-side application).
Here’s a browser-side test case for Axios and SuperAgent: https://jsperf.com/axios-vs-superagent/ and here’s a server-side test: https://gist.github.com/natesilva/24597d954f392b21467b83403756f121
For me, on these tests, Axios is faster in the browser and SuperAgent is faster under Node.js.
I don't really think that it is really speed thing, well sort of. I think it is that Axios is promise based and Superagent is not. They are both asynchronous but since axios waits to resolve the response it gets it appears "slower" than superagent.
I could be wrong though.