The Cardano team has identified and is actively trying to overcome the gaps associated with Proof-of-work and proof-of-stake currencies. The primary issues they are solving for are scalability, interoperability, and decentralization. The team has the right vision in my opinion. Recent attacks on proof-of-work coins and the inherent unscalability of first-gen coins (BTC) are laying bare the drastic need for this new approach. Cardano is not the only project being built toward this goal, but they appear to have solid progress to this end.
CEO Charles Hoskinson has a great youtube whiteboard session posted. search youtube for cardano ceo charles hoskinson whiteboard and you'll find it. It was posted before the massive crypto runup but is an amazing overview of the problems noted with 1st and 2nd gen contracts and will help you understand not only more about Cardano, but also how better to frame your review of other currencies.