Did a bit of testing with a squad mate today.
Plane was the Dr1, I had the govenor off, he had it on.
Mine maxed out at 112 mph according to the E6b, he was getting 115.
And it accelerated a smidge faster than mine.
However, mine would go up to 140 mph in a dive without having to touch engine or throttle.
So you have to ask yourself, is the 3mph worth the hassle or not.
There are advantages to both sides.