Hopefully Mazda really did improve on the six speed Skyactiv manual transmission, the one that comes with the 2.5L engine is apparently not all that great. Very vague. The five speed manual in the Ford Focus feels very solid. The Ford Focus and Mazda 3 both handle equally well but the Mazda 3 has a bit more ride comfort due to its well designed multi-link suspension. The Ford Focus can be optioned with things that you can't get in the Mazda 3 GS-SKY like dual zone automatic climate control and navigation -- you have to go up to the Mazda 3 GT to get those things.
The following I'm stating numbers at 120km/h for informative purposes as most people like to drive this. If you want to meet or even exceed rated fuel economy, the ideal speed is 100-105km/h with A/C off. Of course a head or tail wind could impact this, as with winter gas etc.
The 5 speed manual in the Ford Focus drives at 120km/h at 3,100 RPM. Its highway rating is 5.5L/100km which you can exceed at 100km/h with A/C off. With a 47L gas tank, its range to 25% fuel remaining is 641km.
The 6 speed manual in the Mazda 3 GS-SKY does it at 2,650 RPM. Its highway rating is 5L/100km. With a 55L gas tank, its range to 25% fuel remaining is 825km.
The current champion for gasoline only cars is the Chevy Cruze Eco with it's 1.4L turbo engine... it can do 120km/h at 2,350 RPM. Its highway rating is 4.6L/100km, and if you only want do do 100km/h to exceed those numbers, you'll do it at only 1,950 RPM. With the turbo engine, you have peak torque beginning in that range so chances are you may not have to downshift to perform a moderate passing manoeuvre. However, it has a solid rear axle suspension so the handling just isn't there. With a 47L gas tank, its range to 25% gas remaining is 766km.
For 2012, the Chevy Cruze LT 1.4L turbo will be available with fully independent suspension, but it will cruise at 120km/h at 2,900 RPM in sixth gear. Its highway rating is going to be no greater than 5.5L/100km. With a 59L gas tank, its range to 25% gas remaining will be around 804km.