A lot of complaints recently that Farcaster doesn't have enough "beef".

I'm happy to fight with you.

Bluesky has more users than Farcaster and is also sufficiently decentralized.

What is the best argument for why devs should build on Farcaster instead of Bluesky?

Answering the question "where's the beef?"

Can you say more?
If BS had Frames (which they could add if they wanted) couldn't they do the  same?

The feature would be there but not the users to do it. This is a network of people who are extremely willing to transact in crypto. I haven’t seen another network where this is true. So depending on what you are trying to build, if you want people to use crypto, a community of 100K people who use crypto daily > than a community many times larger that does not.