If you wanted to compare two currencies and compare the level of decentralization, what measurement would you use?
Assuming you could know any information you needed about the number of miners, mining power distribution, number of users, etc.
I will take numbers or miners and mining hashrate power distribution. To ensure if the blockchain is decentralized or not and you can see that from the hashrate (applied for POW). The possibility of 51% attack will be there when there are only a few parties that hold the majority of the hashrate power.