I assert that Nano is the best in terms of technology. It has no fees, is far more scalable than Blockchain based currencies, and thanks to its asynchronous architecture, transactions are fully confirmed in less than a second (under normal network conditions it's currently about 0.2 seconds). It's also more decentralised while currencies based on proof of work or staking tend to lead to centralisation of power. And it's green (no mining).
It does have some tradeoffs. Decentralisation depends on holders voting for a representative (so voter apethy might be an issue). There's also no data field for transactions, though this could be addressed with a second layer (the developers rightly wanted to keep blocks on the first layer as small as possible).
And nobody really knows about it. A bit like Hubski really.
But after actually using Nano to make a payment, no one would go back to using Bitcoin (or any cryptocurrency with fees and less-than-instant finality) for payments where Nano is an option.