Pitches - Splitter, Cutter, Slider, etc

Fall is winding down and October is almost over. Ball players at various levels will start, or have already started off-season conditioning. Later in the off-season pitchers might start looking to for additional weapons for their arsenal like the splitter, or cutter, or slider. I picked these for discussion because they are all thrown with FB armspeed.

Splitter - A friend and I were discussing the potential for the splitter to cause elbow pain. He was unaware. I want to learn more about why. So I've added some links below.
http://www.nytimes.com/2011/10/02/s...-falls-off-the-table.html?pagewanted=all&_r=0
two off-speed pitches [Archive] - Baseball Fever


Cutter - The cutter seems really popular these days with coaches. Almost too popular. Please add any links or discussions about why you like it.

Slider - As pitchers make the transition to college, they learn the slider because they find their curve ball is not as good as they thought. Or it's easier for them to control.

So, I'd like to ask about these 3 pitches...
Which are most effective & why?
Which are easiest to learn?
Which are less prone to injury?
What percentage should they be thrown?

PS. IMO the located FB is the most effective pitch. The first to learn. It's not to be aimed. But thrown hard and accurate. Then the change-up with an effective grip. (notice I didn't say circle-change). Learn the Chg up, practice it with long toss, and bullpens with good deceptive arm speed. And locate it and control it's movement. Then 2 seam FB. Then breaking pitches.

Thanks for sharing.