I pretty much agree with pjf. Training affects improvement/decline of the physical attribute. That's really important.
I use 20m and completely ignore health. I also don't complain when I get injuries because, if I get two recovery cycles, I probably have a better player. People who use ZERO complain. Their 98 health pitcher gets a sore elbow, loses 13 points VR and is out for 98 days.
It's just a preference of how you want to play.