I agree that comments have a better effect than upvotes.
I've noticed that votes on posts tend to be dominated by robots. There is a huge number of bots that upvote right at 5 minutes .... which is the optimum time for getting curation rewards.
Upvoting posts ends up giving rewards to the bots.
I decided to buy enough HIVE to get my upvote above $0.02 (the minimum payout amount for an upvote). The upvote calculator shows the value of an upvote for a given amount of HIVE.
In general, it takes about $500 in HP for an upvote to be worth $0.02.
Of course, my buying HIVE caused the price to halve. Sorry about that everyone.
BTW: When my upvote value is less than $0.02, I will look at the comment section of an account I appreciate and upvote the posts that I can bring over the two penny threshold.
Anyway, my observation is that upvoting root posts tends to reward robots. Upvoting the comments gives a higher reward to humans.