I think Athena sits more alongside 105 and sram rival, so the Shimano build will give you a higher spec group set. However Zondas are a step up from Aksium so the campagnolo build wins there. Given most recommended a wheel upgrade over any other to improve performance then I'd say the campagnolo is the potentially "better", however the £150 difference reduces the gap.
I wouldn't worry too much about the gearing. If you replace the 11-28 on the Shimano with an 11-32 you have a lower gear than the campagnolo for less than £25.
I'm not a pro or high level rider. I can tell the difference between a £500 entry level bike and a £1500 one, but I think I'd adapt to either of the two you describe and not notice much difference in my "speed" or "performance". Like others I have old 10sp 105 on one bike and new Ultegra 11sp on another. When set up properly they both shift well and wouldn't say the Ultegra is better (can't compare braking as the Ultegra is hydraulic disc). Personally my heart would go campagnolo to stand out from the crowd, but my head would go shimano and save 150 quid.
