Either way is good but honestly maybe the 15% for one post per 24-hours would allow you to add more members.
As a member, and someone who usually writes one or two posts per day, the benefit would still be there for me and I am a person who believes in spreading the wealth to more.

And quoting @flauwy... which I 100% agree with...

think to squeeze out another post just to catch that one extra upvote. And I think that can lead to poorer quality posts. It also gives us room to grow.