Here's the response I got from Evans:

Water does transfer heat better, but it also boils and when internal metal temps get hot, the boiling water produces steam pockets in the system that can lead to hot spots in the heads and cylinders.

The Evans product has a higher boiling point, 375F, so it stays a liquid all the time. Consequently, it pulls more heat from internal metals, which in turn, leave behind cooler internal temps. Your gauge won't sense those temps as most gauges have the sensor located near the top outlet hose. So if Evans' coolant is pulling more heat from internal metals, you may see higher temps on the gauge, but the temperature of the coolant is being measured at its hottest point, when it is LEAVING the engine. You are not gauging the temps of the coolant inside the engine.

You may see warmer temps, you may see no change, or you may see lower temps. Way too many variables to know exactly what your car will do. All temp gauges are actually a reference. That sensor for the gauge DOES NOT sit in a still pond of coolant, it sits in a river of constant movement, and that's why you can see temps rise and fall.