Tom Tango posts the results of research into swing rates and run values on swings. He broke the hitters into five groups based on swing rate:

Group 1 swung 57% of the time.  Their overall runs per 100 pitches was +0.07 runs.  Group 5 swung 38% of the time.  Their overall runs per 100 pitches was +0.20 runs.  Now, we don’t know if it’s because they didn’t swing much, or because we happen to have better hitters in Group 5.

TangoTiger.com

Note that group one did not produce the least runs, they actually did better than groups three and four. Maybe group one is represented by Barry Bonds, and group five by Vladimir Guerrero. Tango then does a simulation that has all five groups swinging 38% of the time. All groups improve, but the group five hitters improved the most, up to 0.31 per 100 pitches.

I have heard hitters say something like, you get one good pitch in a plate appearance, and you have to attack it. If it’s not that pitch, you’re better off taking, even if it’s a strike. That’s group one. Group five’s five philosophy would be, swing hard at anything that looks tempting, because the damage done when you connect is worth it. Both groups produce big numbers, but group five could be much better.