For me it was a close finish between Fira Code and RedHat Mono.
I mostly look out for
* no <= or === ligatures (i still like to see the separate characters)
* 'i' vs 'l' vs '1' (I now mostly prefer fonts where the lowercase 'l' has the righthand bend on the bottom)
* dotted zero vs slashed zero (i prefer the slashed zero, but dotted is fine as well)