Just the frame manufacturing technique. Hydroforming gives the designers some freedom makes the bikes tubes shaped better. For example, you can make tubes flatter for better carrying, of varying thickness for better directional ride/stiffness, and the whole frame lighter.
If you’re just using it for CX, it probably doesn’t matter. If you want to use it with road tires, the bigger name bike brands will give you a better riding AL frameset. You can also put a cushy seatpost and bars on it.