JRP,
If both the Milwaukee and DeWalt saws have similar current ratings, e.g., both are 15amp motors, then they should develop very similar power - assuming they are the same voltage.
You didn't state the model numbers but the DeWalt website shows two 14" chop saws as current models. Both are spec'ed at 15amp so they probably develop about 2HP at the cutting edge. Ignore the HP ratings. Those are "Max HP" calculated from the locked rotor amperage draw of the motors and are useless for anything but marketing hype.
The Milwaukee site lists several current model 14" saws. You implied yours was several years old, and I assume, it would be no more powerful that the current models. They are also 120v/15a models. From that, I'd hazard a guess that your two saws should have comparable performance and the DeWalt was sick.
Hope they get it fixed for you.
(BTW, an electric motor producing the 4HP on 120v DeWalt claims for one of the 15amp saws will be drawing considerably more than 25amps - that's why I say ignore the hyped marketing HP)