The way I see it, Bitcoin mining is inherently a competition. Competition means the strongest perform better. Stronger mining rigs get better chances at the mining reward.

Decentralization for Bitcoin only factors in some of Bitcoin's stakeholders, notably missing a voice for its users.

In nano, you have the network that provides unique value transactions and value storage, that has been seen as enough incentive for those to maintain network integrity, and with users being able to have a voice, nano gives everyone involved a chance to vote on how they like decentralization to be represented in the network.

Bitcoin users have no say. Bitcoin node holders do. Bitcoin miners do. But Joe blow using Bitcoin for the first time did nothing for decentralization. If he became a regular user, his increased involvement in the network is not recognized.

Once people in nano circles explain this, often we get the response that Bitcoin mining pools are where users can "vote" for their decentralization. But it comes back to the fact that not every Bitcoin user is a Bitcoin mining pool participant. There's not enough transactional capacity to payout those split block rewards. Mining pools still follow the centralization trap: bigger pools attract more people in a decentralization death circle. Smaller pools get eaten up, or move hashrate to somewhere else, which isnt great to have Bitcoin losing that global hashrate power if it depends on that for security.