The famous study, and what it claimed
Mueller and Oppenheimer reported in 2014 that students taking notes by hand outperformed laptop note-takers on conceptual questions, and proposed a mechanism: typing is fast enough to permit verbatim transcription, while handwriting forces you to summarise, and summarising is processing. The paper was widely covered and the conclusion entered general advice quickly, partly because it is a satisfying story about technology and attention. It is worth reading precisely because it is the source almost every "write your notes by hand" article is ultimately citing, usually without saying so.
What happened when it was repeated
Morehead, Dunlosky and Rawson ran a direct replication with a substantially larger sample and did not reproduce the key findings. Their extension also found that both handwriting and laptop note-taking were outperformed by conditions involving retrieval, which points away from the medium entirely. This is the ordinary and healthy course of a research finding rather than a scandal, but it does mean the confident version of the claim is no longer supportable. We say so here because a study site that repeats a superseded finding to sound authoritative is doing the thing it exists to avoid.
What to do instead of choosing a tool
The defensible advice is about what happens after the notes exist. Notes you never return to have little value regardless of how they were made, and notes you reread passively have less value than notes you use as retrieval prompts. Turning a page of notes into questions and answering them from memory a few days later applies two of the best-supported techniques at once. If the method you use makes you rephrase rather than transcribe, that is a point in its favour; if it makes you keep the notes closed and recall from them later, that is a bigger one. The Flashcard Formatter takes notes in several common layouts and turns them into question-and-answer pairs for exactly that purpose.