Page "Gas giant" Paragraph 15

Unlike the other gas giants, Uranus has an extreme tilt that causes its seasons to be severely pronounced.

The two planets have other subtle but important differences.

Uranus has more hydrogen and helium than Neptune, despite being less massive overall.

Neptune is therefore denser and has much more internal heat, and a more active atmosphere.

The Nice model in fact suggests that Neptune formed closer to the Sun than Uranus did, and would therefore have more heavy elements.