Great question! There are a number of differences, but the main one is in the design and architecture. Stellar and most other blockchain-based projects are primarily designed to displace and replace how the world works. This becomes very clear when you look at Stellar's mission statement:


Hydro is different because it is designed to augment the world's systems. You can think of Hydro like a suite of power-ups for a large financial enterprise (for example), that can be implemented rapidly and broadly without overhauling the underlying private frameworks already in place. We think Stellar is great, it just serves a different purpose!

I hope that answers your question