It seems like a crap shoot to me. We have carved small pumpkins that are just full of seeds and large ones that have very few. I usually just let the kids pick the pumpkins they like and consider the seeds a bonus. We usually have enough from two large pumpkins and two smaller ones to keep everyone in seeds for a few days. I have never found seeds that tasted bad, though.
That's the way I do mine! I try to use popcorn salt if we have it around, 'cause then you don't get the grittiness (is that a word?!) on your fingers.
I LOVE pumpkin seeds. I live in the bathroom between the end of Sept. and Halloween, because that's the only time of the year you can get pumpkins. I buy at least 2 pumpkins/week, just for the seeds!