just to show you what I mean:
This is my Paris-Dakar look-a-like Suzuki DR 750 Big. With it's original low-mounted front-fender and frame-mounted fairing. The bike is capable of something around 100 mph and I think with knobblies on it, a fork-mounted fairing and high fender there would be some influence on stability at that speed. I also own a Triumph Tiger Trail 750 from 1981. This bike has a similiar performance, a few bhp less but same top-speed. In original trim it was equipped with a high-level front-fender that I kept until the mid 90-ies. Then I switched to a low fender. From that day the bike's stability at speed was much better. Although with an old brit-bike you treat yourself to around 60 mph and crack the throttle fully open just from time to time. So there's no fairing on that classic scrambler ... and there's no need for it as you can stand the ton for a few minutes. Then wind and vibration force you back down to 60 mph again.
In my opinion it depends on the bike and your use of it wether you choose one or the other version. The Big is my bike for fast touring on B- and C-roads plus the possibility to leave the tarmac. And if necessary, you can use the motorway at around 90 mph on your trip to the twisty roads mentioned above. The Triumph is better for scratching the B- and C-roads at your door-step. Although I used to do the long trips on it, too, before I got the Suzuki.
Kind regards, Bambi