A larger tire DOES NOT have a larger contact patch. 28 25 23 all have the same size contact patch if all inflated to the same pressure with the same load on the bike. Contact patch only increases when load is increased or pressure is decreased. Don't argue with me over this like other people do. Google it, ask Boeing how they calculate tire patch contact on a runway.
A 25 tire has a wider and shorter contact patch than a 23 (same surface area). This is why it has a lower rolling resistance. The wide patch keeps the overall shape of the tire more round as it turns, instead of having a longer flat spot on the bottom.
It's doubtful a larger tire has better aerodynamics than a smaller one, as the frontal area is larger. The wide rims are generally more aero because of the shapes they can be made into that resist cross wind forces at certain angles. That nice day when you doing a TT a 23 is going to be more aero.
That said, I feel the rolling resistance to aero advantage is minimal on either tire, my coach friend and I were estimating the crossover point is around 27mph. So if you are slower than 27mph run 25's and if you are faster run 23's. We based this on it always seemed like an extra 10watts to do 27 on 25c tires. We did not do this scientifically, it's just an observation.
Buy the tire with the highest TPI and softest casing you can find if you want a nice ride. A 23c vittoria open corsa with a latex tube rides infinitely nicer and has more grip than some 60tpi piece of crap 28c hardcase gatorskin armadillo iron sided anchor. You'll just need to learn to live with a few flats. And also it saves you about 40watts total.
I'm a fan of wider rims that make my 23's more like 24.5's so i save the weight, and have good aerodynamics at wider angles.