One thing the storyline with Data forgot is that whenever you hit his off switch, he's completely off. Switch him back on, he's conscious again, like a computer.
Same thing with the Doctor on VOY and he had much more emotional expression than Data.
It seems like the show takes a materialist view and strongly suggests he doesn't.
And yet on Voy there was an episode with Chakotey where he was out of his body and wandering the ship as neural energy or something.
The shows teeters back and forth on whether there is "something else" out there.