The question of decentralisation is an interesting one. Bitcoin and Eth have both historically run PoW with a small number of miners controlling more than 51% of the power. For a while with BTC there was lots of talk about more than 51% of the hashrate being in China.

When Eth moves across to PoS it is likely to face some of the same issues as existing PoS blockchains.

Other than that I think the questions around decentralisation can be overdone.

PoS decentralisation requires:

1. Geographical distribution of sufficient validators to prevent physical real-world shutdown.
2. Sufficient distribution of tokens.
3. Appropriate mechanisms to ensure staking is spread across validators.

Looking at Solana vs Cosmos:

Solana:

1. Solana has over 1000 validators even though it is one of the more expensive nodes to run.
2. This is where I think the issue is for Solana. 48% is much too high a percentage for founders. But an issue that can be resolved over time?
3. Currently also an issue. Solana has a superminority of 19 due to concentration of staking. But a solvable problem through incentives.

Cosmos:

1. 125 initially then 300 validators (the top 300 by staking from what I understand).
2. Cosmos has a much better initial distribution of tokens. 22% for founders which should reduce over time.
3. Not sure this is a problem given the validator structure. Would need to look into it more.

The question comes down to how much decentralisation is enough. Cosmos looks good to me (once that 22% reduces somewhat). Solana not so much. But potentially all the newer chains can improve their decentralisation over time.