If you're interested in a dual throttle, here is the list of where it will help you;
1. Throttling down one engine to compensate for a missing wing, you can fly straight and level with this.
2. Great hammerheads, you can really squeeze every last bit of energy out of the plane and can reverse very quickly.
3. Immersion (AKAK quote).
4. Spin recovery.
5. Making great 'donuts' on the runway.
6. Out of plane, last ditch efforts (cut one engine and roll it hard).
It will not help you turn tighter, not in anyway what so ever. I have a dual throttle I made and I'm not even using it as it gets me into more trouble than its worth. That said, I'm going to buy myself the Thrustmaster Warthog when it comes out... I'm a glutton for punishment, I guess.