The Honda 1.2 would me more effiecient because of its lower displacement engine, but has less power, so if you have a heavy foot you'll likely to consume more gas on the 1.2 than the larger counter parts.
if you want the most effiecient car available in the market today get the sub compacts like
Kia Picanto, hyundai gets or matrix crdi diesel, toyota yaris, cherry QQ just to name a few
youll save more and be free from headaches when getting a brand new car
because obviously new engines are more effiecient than used ones