I Bowl with old timers still using the LT-48 and older stuff, these things are built like Tanks. Many have chunks out of them but still work well for spares, a few geezers actually throw so slow that the ball still hooks for a strike ball.

Plastic to me is worth two years tops, I am on year two of chunked up Crystal diamond it actually needs a total resurface but since I use it for spares only I leave looking like crap instead.

I have a Century 21 Rubber bowling ball.
I am a Full Roller and my Rubber ball is drilled with the aggressive Full Roller drilling for pancake weight block.
This layout uses a balance hole that is 4 1/2" deep and 1 1/8" in diameter.
My ball balances with zero top and zero side weight.
The balance hole allows the ball to get about 3-4 inches of flare.
This layout was designed by Ron Machniak of Precision Bowling.
http://www.precisionbowlingproshop.com/

Having said that, this rubber ball can have a stronger reaction that my urethane bowling balls. If the lane is not too oily or has a good dry backend then this ball will grab nicely and carry very well.

The filler of this ball actually looks like a combination of cork or particle board and rubber bits.

Here is a video showing how it reacts on a lane that has a fair amount of oil in the middle but drier sides and backkend.

Who says rubber can't carry?!

https://www.youtube.com/watch?v=iYdfF4m_Kxs

I still use an old Rubber 1980's Black Beauty for my Spare ball... It is all dull, and with normal shot it will hook only a few boards the entire length, very predictable unless the lanes are super burned up or just dry.   I did have it hooking really good a few weeks back when everything was just too much.    I use a fingertip just like every other ball in my bag, as when I had a conventional grip on it.      For the first time ever I got a white dot Columbia 300 to eventually replace it on lanes that are super burned up.