I'd suggest going with a Rule. If it's too much ball, you can always polish it up with some Magic Shine. It's an awesome ball for med/heavy to heavy oil conditions. It might be a little too much for medium oil patterns, but you can always move deeper or lightly polish the ball.
Another option is to get the Rule and if you're unhappy and/or need more length, you can always get the Xception after.
I'm sure both balls complement each other very well, however, getting both at once because of an impulsive and undecided point of view seems to be a waste of money.
Hope this helps!
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-Dino Sia