First of all, if you are deciding between the 3.4 and 3.4ARs, the choice is dead easy IMHO: just get the ARs. Even if you decide to stick to 25 mm rubber, you can still mount them on the wider ARs without a big aero penalty. And you could go far wider than 28 mm if you wished in case it is warranted (e. g. for light off roading or off season riding where safety may be more important than minimizing rolling resistance).
Before I comment on the arguments you bring forth, let me bring up a few points you haven’t mention, but that I feel are important:
- Wider tires provide more grip, which translates to better braking and faster cornering — especially in difficult weather.
- Wider tires are not just more comfortable, but safer as you bounce around less. This is important when you frequently encounter less-than-perfect road surfaces, where narrower tires pumped up to higher pressures can get a bit “jumpy”.
- You have way more options when it comes to adjusting pressures. I run on 28 mm Corsas when the weather is nice and 28 mm Corsa Controls in the off season. During my last race, it was raining buckets. I was really glad I could lower my pressure to 63–65 psi. Rolling resistance <<< not crashing.
Now let us have a look at your arguments, and your conclusion rests crucially on your assumption that 60 psi on 28 mm is equivalent to 80 psi on 25 mm. Fortunately, since you are deciding between two Enve wheelsets, this one is quite easy: Envy has a list of recommended pressure as a function of rider weight. I don’t know how much you weigh, but for the sake of argument, let me assume you weigh 73 kg. Enve’s recommended pressures are now as follows: for 25 mm it is 63 psi, for 28 mm tires it is 53 psi. If you scroll through the list, you see that generally, the difference in recommended pressures is 8–12 psi, depending on your weight, with the difference increasing slowly with rider weight.
Bike rolling resistance does not go down to such low pressures, they only measure 60 psi, 80 psi, 100 psi and 120 psi. However, you could take the lowest figure, 60 psi for 28 mm and interpolate the rolling resistance for the 25 mm tire. You see that the 28 mm performs about 0.5 W better (using my eyeballs). So that suggests that also at Enve’s recommended pressures you’d be better off with 28 mm tires.