it depends on how big that window is, how much sun it gets, how close the seeds are to the window.
it also depends on how big the lights are, how much light output and so on too.
natural light will always be better than artificial light. a fluorescent bulb can only produce so much in the light spectrum, while the sun has many spectrum's including ones we cant see.
For all things come from earth, and all things end by becoming earth.