How does Proof of Stake (PoS) improve scalability compared to Proof of Work (PoW)?
Scalability is not related to algorithms, Proof of Work, Proof of Stake. It relates to two other things, block time and security. When you increase one factor, two other factors will be affected in a Triangle.
There are Proof of Work blokchains with big block size that is good for scalability like Bitcoin Cash, a scam altcoin, but you can see demands on Bitcoin Cash blockchain is very low, not comparable to demand on Bitcoin blockchain.
In security, it is very worse compares to Bitcoin.
https://howmanyconfs.com/6 confirmations on Bitcoin blockchain that takes around 51 minutes, will be equivalent to 1,130 confirmations or 7 days and 17 hours on Bitcoin Cash blockchain. Do you see big difference now?
What are the environmental advantages of PoS over PoW, particularly in terms of energy consumption?
For security of your fund, do you pick a safer one or a more risky one?
PoW or PoS is only an algorithm, the bottom line is always your fund safety.