How are lightbulbs manufactured differently to a certain number of watts?

Question

What do manufacturers change about an incandescent lightbulb to make it consume a specific amount of energy?

Also, does anyone know whether a 110V or 220V lightbulb at 60 watts would last longer (or equal lifespan) and why?

Answer 1

It's the resistance, which is dependent on the filament's length, thickness and material.

Answer 2

It has to do with the thickness (gauge) of the filament wire.