For me it's the overall vision and roadmap. I would argue it's the only cryptocurrency project that sees itself being able to scale to millions of txs/sec in a decentralized manner. Another thing that makes it special for me that is probably less relevant to new people finding the chain is how it has endured and survived to get this far. I believe that's only because the leaders of this project truly believe in the mission of separating money from the state and how that could change civilization as we know it.