Not only is Razr M Faster.. it can also be Updated to Android 5.0L Lollipop [CM12]. Tough its a wip rom.. Its been my daily driver since 2 months now and haven't had any issues.
So go for XT907 Razr M.. Battery life is on par with any other cellphone in this range plus SMOLED Display.. Crisp snaps and videos. What else you expect from a 9K cellphone?
And about Camera.. I've used Electrify2, RAZR M, Razr XT912, Razr HD.. All have pretty much the same Results with only minor difference though a 2-3K difference in price.. SO if you need a bigger screen why dont you go for a LG Optimus G/ G pro?