Answer:
I prefer leaving the answer as √5 since it is a shorter form and exact form of the answer.
Here are reasons for leaving it as a radical form or a decimal approximation.
If you are looking for an exact answer, then you should leave it as √5. For example, if you are told a square has area 5 square units, then the exact length of the side is √5 units.
If √5 is the length of something that has to be made to that length, then you need an approximation. For example, if you are asked to make a square out of cardboard whose area is 5 square feet, then you need an approximation of √5 ft, such as 2.24 ft, so you can make each side of the cardboard square in the length of 2.24 ft.