Steve,
Thanks for the great suggestion! I reached John Clark and had a really nice chat with him. I thought I'd share the key points, as they were surprising.
An Allison equipted coach will be 4 ~ 5 seconds faster than a ZF to 60mph, as the drive train is always engaged, while the ZF clutches between gears (actually using the brake retarder on the engine to bring the rpms down to shift faster). The Allison will also have service outlets throughout the U.S., where the ZF will be much more limited in servicing options.
The ZF will perform better on grades (up and down), as it has so many more gears to choose from and the "jake brake" is much more powerful as a result. Mileage advantage may be a bit better on the ZF, but the Allison does lock up the torque converter on overdrive gears, so it's not a huge difference.
As for that rolling back at stop signs on a ZF, that's a driver controlled option. If they push hard on the brakes at the stop and then let up slowly and completely, the front brakes lock "on" and will remain on until you accelerate, which takes them "off" -- but if you don't push hard, they won't lock.
So it kinda comes back to what type of driving style you're most comfortable with. If you like driving a stick with a lot of control, or climb a lot of steep grades, you may be most happy with a ZF. On the other hand, if you live/travel in the flat lands, or like drag racing off red lights, the Allison is your best bet.
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