Waves is one of the most promising and worthwhile altcoin to invest. However, if you choose between Waves and Cardano then I would definitely choose Cardano, because for me Cardano is better. Cardano has the perfect blockchain technology, professional development team. Cardano overcomes many of Bitcoin's weaknesses and shows that the altcoin is well scalable. I believe that long-term investment in Cardano will bring us a lot of money in the future.