@Gaara♥. That's a matter of opinion.

Physical Fires are limited in their abilities and unfortunately unable to attack more than 2 enemies in a single turn. Fire FS is basically like using Arrow Rain, without the need to equip a Bow. Arrow Rain is Water-Based damage, while Fire FS is obviously Fire-Based damage. Fire FS is capable of Critical Hit damage, and could prove to be very useful if you don't have a Crescent Bow, a Bow with a Crit Diamond, or simply just don't have time to equip a Bow during battle.