With a standard round ball with no handles you risk dropping the ball at any time or having it slip out of your hands due to slippery or sweaty hand conditions and bashing something close by such as a lamp or anything breakable

A doublehandled ball just makes all the sense in the world

The whole purpose of any exercise is to receive the benefit of having don

Or you have to concentrate on maintaining your grip on the ball instead of thinking about your form on the particular exercise you are doing