I think both cues are helpful because they really explain two different but related things.Instead of "letting it get deeper" cue which I have used and explained, I have been using "keep your shoulder closed a little longer". Seems to work. I believe the more the hitter understands their swing and more they own it the better.
Letting it get deeper is about recognizing the pitch location. Keeping the shoulder closed longer is what you do once you've recognized location.
The first is the "what" and the second is the "how." I think you need both to truly be successful.