The "Chief" control systems and Legacy are really aimed at different markets. If there's some crossover by the Legacy folks, it makes Lionel happy.
The simple fact is conventional control as a marketable scheme for Lionel has sailed into the sunset. Lionel's O gauge starter sets aren't even able to be run conventionally, they don't have the conventional slide switch built in and there's no way to add it. And all MTH sets use a stripped down DCS command system, although their locomotives still can be run conventionally and also have full featured Proto-3 in them.
After playing with a friend's GP7, the FC sound is OK, not a good in comparison as MTH's Proto-3 or Lionel's Legacy, but OK. But, I'm neither here nor there about sound, I've even turned the sound off sometimes when running. But, FlyerChief does offer smooth operation and control, something I care much more about than sound.
If I was still interested in buying traditional type Flyer, the FC system wouldn't be a show-stopper for me.
Rusty