Somewhat depends on how you roll the ball, I destroyed plastic balls for years because I track right up next to, or on my thumb hole on my spare ball, and when I had a switch grip in they cracked even sooner than with just a normal slug. I have not had any issues since switching to urethane spare balls (have one of the newer Motiv Sniper currently)
I would recommend as mentioned earlier the Storm Mix, or the Motiv's Sniper (think the current one is midnight?), they would convince you they are plastic in most cases and a durable as all hell.