Everyone above is correct. 30 (or possibly wider) is the better option if you can match the wheel profile to your tire size. You’ll pay an aero penalty for going wider than your wheel though. It’s not enough to rule out other considerations but could make a difference in certain conditions.
My vote is 28 front 30 rear. Front wheel takes a bigger aero hit, and rear wheel carries more weight (and therefore transfers more vibration). Do check first and make sure a 28 actually inflates to 28 on the Foundation rims - a bit of searching should find someone that’s measured that combo (or at least on a wheel with the same internal rim width).
I change my vote to 30/30 if you anticipate riding in tight formation over bad roads for the bulk of your events - in that case you’re drafting more and also less likely to be able to pick an ideal line so extra cushion up front becomes more valuable.