I can give you a bunch of reasons, and will in a bit, but the most important advice I can give you is to test some wheels of varying depths to figure out what you like most. Ask friends to borrow their wheels and ask your local bike shop if they have demo wheels. Riding the various wheel depths will let you feel how each is different in wind and weight. And while there will be some differences between different brands/models of the same depth, those differences will be less substantial than the depth differences.
In the case you can't sample some different sizes, here's some generalized advice.
More depth begets more crosswind deflection. 25mm is close to basic - the depth of an average alloy rims. Since you mention Zipp 303s, I'm deducing you want carbon wheels, in which case 25mm doesn't get you much aero efficiency, but is usually quite light. 303s are 45mm deep, and you'll find most people are comfortable around the 40-50mm depth. It gets you aero efficiency without too much crosswind catch.
Deeper is more aero. Deeper is heavier. Deeper is more crosswind deflection. Generally, aero efficiency gains trump the extra weight you take on for deeper wheels, but you have to consider how much climbing you're doing and the crosswinds.
Considering your weight and terrain, (rolling hills), I think you could go up to around 50mm depth, but will probably be more comfortable around 35-40mm.
Make sure to read this article, too: http://www.bikeroar.com/tips/going-aero-5-things-you-should-know-before-buying-aero-road-wheels