Narrow bars don't make any difference worth mentioning in "twitchiness" of handling. If anything, they improve stability. Look up a picture of track racers doing a madison sling, and make a note of where the slinger's left hand is: on the bar tops next to the stem. This is because they can put a lot of pull on the bar from that position without moving the front wheel very much, which would obviously be a problem. Or if you ever want to push another rider, up to a wheel for example - the most stable position is with your hand near the stem. Try it with one hand on the brake hood and you're likely to have a hard time to avoid falling over. The flip side is that wider bars will give you more leverage to move the front wheel more easily to make steering movements. This is why wide bars might be desirable on a loaded touring bike with a relatively heavy front wheel. It's easier to make steering adjustments against the inertia of the load you're carrying on the front wheel. Wide bars can definitely make certain kinds of bikes under certain circumstances easier to control, but when they do it is because they make the steering MORE responsive, not less. And the other side of the coin is that sometimes narrower bars will make the bike easier to handle. It's all about the specific situation.