Which is better for the straight lines next to the corners of the mouth, Botox or fillers?

A straight wrinkle has formed next to the left corner of my mouth.

Looking in the car sun visor mirror in broad daylight, it looks darker because there isn't one on the right side.

Which is better for the straight lines next to the corners of the mouth, Botox or fillers? Would it look unnatural if I only did one side?

The warm words of those who have undergone treatment for wrinkles around the corners of the mouth

I would appreciate your advice.