I don't carry a spare ball, I just flatten out whatever ball I'm using for strikes. I can't get the same feel switching balls. If I had to get a spare ball, I would use urethane since plastic squirts in the oil for me.
On the other hand, I do from time to time bowl two handed and I do not have enough speed to throw resin. I know it defeats the purpose, but while I am learning, to keep the ball in play, I will throw anything from old old plastic to urethane. On ths I ave 190 with urethane but 130 with resin. When bowling two handed I shoot my spares one handed with urethane.
For my strike ball two handed I have used anything from an original blue dot (over 30 years old and hooks less than the white dot) to a white dot, buzzsaw xxxl (plastic with core) to two piece urethane (original blue hammer). I don't know if it the cover or the core, but the xxxl hooks a lot more than a white dot. On bowlingball.com all the plastic balls are rated a 5 on the hook scale but the two piece plastic taboo spare is a 50. So I'm guessing some plastics hook more. I think cause of the core, my xxxl also hits harder than a 3 piece plastic. I also have one of newer generation urethanes (storm natural), but that ball goes way farther down lane than my blue hammer.
Since there are times when I need to throw plastic, I am also considering a true blood to replace my xxxl.
