Brainscape confidence buttons versus Anki's scheduler - has anyone noticed a real retention difference?

Ran both through two exam cycles and my honest answer is that the scheduler difference was small enough that I could not see it through the noise of how well the cards were written. What is not small is control: Brainscape's decks are convenient and you cannot restructure a bad card into three good ones, edit at scale, or take your history with you. Anki's modern scheduler will also adapt to your own answer history rather than a fixed ladder, which matters most on the cards you keep getting wrong. If the shipped deck is good, use it; just do not expect the algorithm to be the thing that saves you.

Disagreeing with the premise a bit. Scheduler choice is a small fraction of outcome, and the variable that dwarfs it is how aggressive your intervals are relative to what you can tolerate - people who set a high retention target do far more reviews for slightly better recall, and people who set it low feel efficient and forget things. Decide what percentage you are willing to fail on first. That single choice matters more than which app you use.

Do not trust either app's self-reported statistics for this comparison - measure it yourself. I kept a sheet: once a week I took twenty random cards I had not seen in at least seven days, answered them cold on paper, and wrote down how many I got. That gave me a comparable number across two apps with completely different definitions of a review, and it turned out my Brainscape decks scored worse for a reason that had nothing to do with scheduling: the questions had multiple plausible answers.

Use whichever one you will open on a Tuesday when you are tired. Everything else is a rounding error against that.

I spent about six weeks tuning Anki's options, reading about scheduling and rebuilding my deck structure, and I studied less in those six weeks than in any comparable period. The tuning felt like studying. It is the most seductive form of procrastination in this hobby and I would not have believed that about myself.