Ask HN: What's the best open source alternative to IDA Pro?

Ghidra: https://ghidra-sre.org/, https://github.com/NationalSecurityAgency/ghidra

Upvoted because I'd like to see an answer to this question too.

I've heard a lot about IDA Pro but I've never used it. What are the most important functions it has that you can't do with, say, gdb ?