This may help you out. For reference, the Afterburner has a symmetrical core and based on the picture, it appears to be similar to a 3-1/2 x 5 x 3 layout with a higher track.
With a 13-14 or 15 mph speed, you would probably benefit with a hybrid cover. This way, you still get good length while getting an earlier read on heavier conditions.
In the Ebonite brand family, you may want to check out the Ebonite Endure. This ball has a stronger hybrid cover that is designed for medium-heavy patterns. It's still a symmetric core and will react a little earlier than the Afterburner.
The Storm Hy-Road is one of the best hybrid balls available. It also has symmetrical core, proven hybrid cover, is designed for medium-heavy patterns, and should also work really well. Also, it may be slightly lower in cost than the Ebonite Endure as the Hy-Road is not the newest tech available. Basically each time Storm tries to discontinue this ball, it keeps coming back as the newer stuff doesn't exactly match what this ball can do.
Since both are symmetrical, you can most likely use a similar layout to what you have with just some minor tweaks. Also taking into account the lower rev rate and wrist, these would allow you to play a very similar line with only minor adjustments.
You really can't go wrong with either choice.
