What is the noun in the phrase obedient faith? It is faith.
What is the noun in the phrase faithful obedience? It is obedience.
What is the difference between the two phrases? The first shows that a person is obedient to the faith found in Jesus Christ: His mission, His teachings, His direction, His __________ anything. The second shows that a person is determined to be obedient for obedience sake. Now, the difficult thing with this is that the obedience that these people might be faithful in may not be anything close to the understanding that Christ had intended. In fact, the trust found coming from the second phrase focuses on how good a person is at keeping "the law" (or their tradition). Their trust then is in law keeping itself; rather, than Jesus Himself - this is damnable (cf. Galatians 1:8; cf. Romans 1:5; 16:26).
Jesus does want His people to be obedient to Him; however, He nowhere teaches that anyone is saved by faithful law keeping; i.e., trusting in their own ability to keep the law. Rather, Jesus wants His people to be obedient to Him, trust Him for salvation, while at the same time living a Christian life.
Show your respect to God and be obedient to the faith of Jesus Christ.
The Lord's humbled . . . John A. Reeves
Please read my article "Polar Opposite" for more detailed understanding.