Also a 90kg rider, with two bikes - one with shallow wheels (25mm Ksyrium S), the other with deeper carbon (Light Bicycles 45mm). The deeper wheels, being carbon, are actually lighter than the alloy Ksyriums.
I rarely notice the breeze on the Ksyriums. headwinds, crosswinds - that bike is unflappable. Crosswinds rarely impact steering feel. The Ksyrium S wheels replaced a worn out set of Ksyrium Equipes (SoSmellyAir, I think you participated in that discussion), and the newer wheels put a bit more pep in my Bianchi's step. Given that it's a shallow alloy wheel replacing a shallow alloy wheel, the difference really could only be attributed to the ~250g drop in weight. The bike feels lively, and is does rolling or technical terrain well. Oddly enough, despite being the heavier bike with the heavier wheels, the Bianchi can claim many of my uphill PRs. Going downhill, she might not be quite as fast (chalk that up to not just wheels, but rim brakes and less descent friendly geometry), but she handles slaloming down winding roads with ease. The deeper wheels occasionally take a bit more effort to turn, which I generally chalk up to aerodynamics of some sort.
The 45mm Light Bicycle wheels replaced some 30mm Vision Team 30s, which were 1900g and felt like lead bricks. The Light Bicycle wheels saved about 500g, and my (new-ish at the time) Lynskey went from being a disappointment to being sprightly. That said, the 45mm deep wheels feel a little spooky when crosswinds pick up. There are times when I want to make a line correction, and subtle, subconscious shifts to steering actually produce significantly more resistance than expected. There's always the momentary "Am I tramlining? Do I have a flat?" thought before remembering - oh yeah, deeper wheels and a crosswind. Has it ever blown me off course? No. Have I ever felt they were a danger? Also no. Do they take getting used to on windy days, especially when going quickly? Yes. In a headwind, I feel like I can maintain forward momentum better on the deeper wheels. Even without headwinds, on flat terrain, the deeper wheels seem to make it easier to keep going. Do I have watt meter measurements over a closed course? No.The difference is subtle, but having spent $1400 on the deeper dish wheels, I have to believe it's there :-D
TL;DR: shallower wheels work in all situations, and I'd call them more 'fun.' The deeper wheels feel faster.
If the conditions are variable (some hill days, some flat days; some still days, some gusty), and if the budget allows, I'd consider getting a spare front wheel. Go for ~50mm, but trade out to a 25mm if you plan on a lot of up, technical downs, or if it's windy. Though keep the same hub and brake rotor to minimize any fiddling needed for that.