To me any drill that enables hitters to take more fundamentally sound swings is great whether it be a batting tee, soft toss, swift stik, hands back hitter, BP etc.
But in my opinion, the best way to build core strength, bat speed and bat quickness is nothing more than tossing it up and hitting a line drive as hard as you can (with a slightly heavier bat like wood). I call it “self toss”.
It’s fun and challenging and also teaches plate discipline. Both of my sons did it (and long toss) for 2 months on alternating days every off-season.
The results were measurable each season. My son that is still playing in college does it every time he goes to the cage. He can work on hitting the ball hard to all fields without depending on an accurate pitcher.
If you have never tried it please do. I have never met anyone who tried it that did not like it. However I have encountered a few folks on the Internet who have not tried it that didn’t like it.
THop