This question was asked by me a few months ago and John Cobb himself actually replied telling me that the road version simply has more padding.
To find the thread, do a search for Adamo Road and posts by "TriBodyboarder".

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My business-eBodyboarding.com

I exchanged the racing for the road some time ago, in my eyes the differences were

- the road had slightly wider rails at the front (this was a big issue for me in the racing, where the front was too narrow thus still causing numbness, this was the reason why I exchanged it)
- the road is slighly more padded and so slightly comfier (although the racing one was already comfy enough for me)

The road is ~5mm wider at the prongs and its softer at the rear.