I've got a question for you... single spare shooting or more pins?
Rubber ball would probably be fine if it's mostly single pins, but I've noticed over the years, some of the newer stuff seems to have more hitting power. Not sure if I worded it right.
From the lady who can't spare. (smile) I bought a plastic just for the ten pin. Everytime I make it, I hold it up and go, the $60 was worth it. My ave. went up 11 pins this past year. Now to learn to use it for other spares.
With my old eurethane 10 pins weren't a biggie, but when I went onto the newer stuff forget that.