What's convinced me to invest (5-10 year hold time) is the fact that they base their development on peer-reviewed research. The founder seems like a really intelligent and careful guy, likely related to his strong affiliation with the founding of the ETH network. Cardano is notoriously "slow" at developing but that is because their core philosophy is to take their time coming out with infrastructure and launching only when it is ready to go, contrasted with Ethereum which launched quickly and planned to patch it when needed. Whether this "do it right the first time" approach means they will be the most popular form of crypto, or if it means they will fall behind those that rush their projects out and push patches when problems are found, is anyone's guess, but I personally agree with Cardano's philosophy of doing it right the first time despite the increased waiting time required to launch. Furthermore, smart contracts are on the way (popular phrase, amirite) and the Cardano network is growing at a fast pace.