Your choice of a shaker is usually guided by the tone that is appropriate to the music. Sometimes logistics and convenience must have a say in the decision. A spherical (round ball) shaker can be a handy friend in some tricky settings.
With prism and cylinder shakers, you have to make sure that the instrument is parallel to the floor for a "straight feel." With a sphere, it is not so much of an issue.
Recently I had to play (LIVE) a shaker pattern with my right hand and a cajon bass / slap rhythm with my left. The shaker in the picture worked great...a good timbre and I could give my attention to the cajon without having to think much about the shaker angle.
One more thing...in a quick instrument switch, a spherical shaker can be easier to pick up and move into playing position.
I keep this one in my mallet case.