Booming Blade's damage scaling is the same as Toll the Dead, but with a smaller damage die.

However, since its effect depends on a weapon hit instead of the elf spellcasting ability (intelligence), I suspect it will proc more often than Toll the Dead for most melee Fighters. Seems like a good choice if you want to your cantrip to be for combat.

On the other hand, since a fighter has plenty of weapons for doing damage, you might consider picking a utility cantrip instead. How often you use it would depend on your play style and DM, of course, but in my experience, all it takes is a little imagination to get tremendous value from utility cantrips.

Here are someone else's thoughts on the wizard/elf cantrips. Keep in mind that they're probably considered in the context of a wizard casting them, rather than a fighter, but the points noted there are worth considering regardless.