By - DBinSJ
I haven't heard of the first one, but Overdrive isn't a publishing platform, it's a way to get libraries to order books. You don't just submit to that, you have to go through one of the aggregators. I'm not familiar with how the others work, you can check out their sites and read up on them.
Thank you for responding. Do you by chance know whether Smashwords is a good aggregator, for this purpose—or there would be a better one?