Depends on the more on the lenght of the oil on the lanes you will be playing.
I sometimes used urethanes for sparing. On long oil, with speed the urethane will behave like a plastic ball and offer no bite. but on shorter oil, the ball will start to turn, albeit only a slow, soft arc. I usually keep my urethanes in the 1200 grit range, and sort of let it roll onto the pin/s. Shiny and it might suddenly turn at the last moment.
Hope this helps.
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DARK BEER IT IS THEN!