The main difference is that sidechains always rely on a certain third party, while LN can be custodial. I'll repeat what I said during high fees in 2017: I don't care how Bitcoin scales, as long as it does it.
Even if Bitcoin turns centralized in the long run? Scaling should be done in a responsible manner to help prevent BTC losing its core aspects of decentralization and censorship-resistance. Why do you think chains with a big block size (BCH and BSV) didn't succeed? Because they chose to sacrifice decentralization in favor of high performance and cost-efficiency. Layer-2 networks like the Lightning Network are a much safer bet. Even though the LN is flawed by design, it's a temporary solution meant to scale BTC without driving it away from its decentralized principles. If the LN shuts down or gets compromised, the main BTC blockchain will still be running as usual.
Developers need to get their act together by focusing on fixing the LN's issues to make it a reliable scaling solution for all. Improving UX (user experience) is the first thing they need to do. At least, we have plenty of options to choose from. If you're in a hurry and want to save money, why not use an altcoin ("shitcoin") instead?
