I own an NA Miata, a 2007 Mazda3 2.3L and a 2012 Focus 5-speed. I like my new Focus quite a bit, with a few caveats. You should be your own judge. Here are my impressions:
The shifter on the Mazdas both are more precise and have shorter throws than the Focus, though the Focus manual is still very precise (no complaint). Engine-wise: the Focus is quick, but doesn't feel it (it feels somewhat isolated). The Mazda feels faster/responsive (though it may not be) with better torque off the line.
Handling: I find the 3 to be quicker and more nimble feeling (with much better steering) than the new Focus. To me, the Focus feels more like a VW Golf (very Germanic) but the 3 is more out-and-out fun to drive. To be honest, I'm not in love with the electric steering, etc. Sometimes, it feels unnaturally heavy and not as linear off-center as I would like.