Manual curation is best and it increase with good visibility of posts on steemit. Definitely UI of steemit plays very important role here. I have started manual curation when I joined the platform , but lost interest as most of the posts are in trending by bidbots and website is lagging too. Although @partiko some what played good role in mobile experience, there is still need a lot of improvement. Curation should not be feel like a great task here, it's should be so simple. So people spend more on steemit to go through content rather than only checking their post every minute to watch increasing rewards.