Both bonds result in forming of differentiating properties and structures. Atoms react in order to achieve stability.
However, covalent bonds have a unique property that ionic bonds do not have, and that is occurrence.
Unlike ionic bonds that only react between a metal (cation) and a non-metal (anion), covalent bonds are strictly non-metals and non-metals.
Ionic bonds involve the cation "donating" their to the anion, resulting a strong chemical bond. This leads to many different, beneficial properties.
Covalent bonds share electrons, forming pairs with other atoms. This can lead to complex molecules such as glucose,
Additionally, the sharing of electrons is very weak compared to the those in an ionic bond. also have a property of being polar and non-polar, something don't have.
There are a lot more, but I've went through the basics.
Hope this helps :)