Hot lime soda requires hardly 15 mins. Hence it is more economical while cold process requires several hours.

Dissolved gases like $O_2, CO_2$ are removed.

Due to high temperature, bacterial contents are minimum.

Iron and manganese salts are precipitated out because their content is reduced.

As the chemical reaction is faster, the precipitate settles faster, since the amount of coagulant if added is very low. And for above reasons, hot lime soda process preferred over cold lime soda process.