Batter #1 is going to improve his skills if he uses deliberate practice. Where Batter #2 is just going through a warmup drill. Are 5 swings enough to improve muscle memory? Trying to work on too many things at the same time means that you'll remember little of what you were trying to improve. Part of the hard aspect of deliberate practice is forcing yourself to try and improve something that you think you're good enough at. Really it's a matter of where someone is in their skill development. Someone like me would need to focus on the basics. An advance player would get more for their practice time working on advance skills. Another issue is how good do you really want to be at a static skill. Hitting a non-moving ball is a practice skill. At the US Open every year I see kids beat Roger Federer in a target hitting contest, yet in a real game they wouldn't get a single point against him.Batter #1 would be better at the skill he's working on, but Batter #2 would be a better real player because the skill he's working on is being more flexible to real batting situations.The key is that no matter what skill you try to improve, you work hard enough that you push forward some improvement. I think that one of the biggest errors people make is to work on too many things in one practice. A second problem is when they move on to something new too quickly.