I watched 5th Gear's review about both cars. Not comparable imo. The Mazda 6 is a midsize car as opposed to the Lancer which is relatively a small vehicle.
What is nice about the Mazda6 is the fuel economy figure owning the best consumption of 55 miles/gallon compared to the Lancer that can only deliver a reasonable 44 miles/gallon.
Mitsubishi Lancer?

Mazda 6?
I'd pick the more Earth-friendly, more spacious and comfortable vehicle.