I currently have a 7'1' M MOD TOURNAMENT ZX. am i better off with a 6'9" m fast?

If you want a fast action, yes.

It depends on where it fits in the arsenal.  If you want a rod to throw small to mid sized cranks, and traps or maybe even some square bills and spinnerbaits, then stay with what you have.  If you have a different rod that throws them well, then the 6'9 m fast makes sense for throwing jigs and creature baits, in fact any 1/4 to 3/4 ounce texas rigs.  It should also handle things like small to mid sized spoons or blade baits like Silver Buddies.

These two rods fill very different purposes.  Do a Tackle Tour search for a Powell Max683 CEF and read what they say that rod did well, now forget the fact that they tried throwing the heavy 2 ounce swimbait because they admit that the rod was not designed for it and they were amazed it handled it. But for tx rigs, jigs, and even some rip baits it played well. It is typical of what a rod with those specs can be expected to do.