Each one has its upsides and downsides. Kbin’s search is more convenient for certain use cases, but it suffers from the same problem as Reddit’s search - it always sorts by new no matter what. In addition, it can only index instances with which kbin has federated. FediSearch should in theory index every instance, regardless of federation status, and do so in such a way that the most useful posts show first (assuming Google does its job).
I will absolutely check this out, thanks for the suggestion!
Edit: I can’t get searx working at all for me, but I went ahead and implemented whoogle support