“Which is better: internal focus vs. external focus?” is a pointless argument. It’s like the old “what is the deadliest martial art?” question.
Different people learn differently and the correct cue is the one that gets the desired response from the individual.
External focus has its place, but in my real-world experience, more people learn NEW skill from internal cues of body alignment, positioning, etc than from loading them up and letting them go. This is true for both elite athletes and general population. After all, we are all humans and we tend to be more similar than different. This includes HOW we learn.
For an intermediate level of skill, once alignment, positioning, breathing, etc are no longer a conscious checklist, the load can teach things that cueing cannot. Here is where external focus becomes more useful.
For refining and improving an existing advanced skill, internal works better. Understanding and feeling the internal workings of your own body is one of the most crucial aspects of deep skill.
My conclusion, based on my own training and my students: Both are important.
If we focus ONLY on moving the weight from point A to point B, then our body seeks to find the most efficient way to get it done. As weight gets heavier, technique will degrade. If we focus on technique first (internal) then the line of trajectory is more consistently the same and as the weight increases we get stronger in that movement.