It's a high baffle mpc, so the M9 would be better yet. You need an open tip to balance out the high baffle unless you want a thin shrill sound. Caveat: My subjective opinion, based on my own experience with a number of high baffle mpcs, although I haven't played a Metalite.
You haven't played a Metalite, still you recommend an M9 over an M7? Strange. Based on what? Presumption?
If you follow that logic, why not say the M11 is better still?
To the OP:
If you are on a 0.90, which is in the ball park of an M5 at 0.95, an M9 at 0.115 could be a bridge too far IMO.
I can make an M9 work, but it takes much more air and work and sounds "duller" than an M7.
You also seem to contradict yourself saying you want a cleaner, yet bright but raspy with some edge. Bright, raspy with some edge seems the opposite of clean to me.
Anyway, they are cheap, but good mouthpieces. High baffle does not directly translate to "shrill". It is just one of many factors that determines the sound.
If you like a mouthpiece with "zing" you'll need to fork off more cash.
Try them all. The proof of the pudding... you know.