You're really working way too hard to try and find some possible advantage for the Subaru. While AWD might be a deal-maker if you live in the wilds of snow country, for most people it is totally unnecessary and merely adds complexity and weight. Meanwhile you are comparing an unattractively designed Subaru with a questionable powertrain versus a Mazda that is generally considered a most satisfying car to drive and which looks pretty cool. It is no contest.
You see what happens when 170hp goes to 148hp?!?
AWD adds weight and complexity, yet the 2012 Impreza weighs less than the 3 without. Sure it adds complexity but so does a telescoping steering wheel or a independent rear suspension. Complexity is the wrong measure here, I think durability/reliability of a component better gets to the real consumer issue and I think as far as AWD goes Subaru does good here.
I of course agree the 3 vs Impreza is no contest, but in Subaru's favour after alternating between a previous gen Impreza and a 2010 3 GS for daily commuting duty 120km round trip for one year. Feature-wise both are similar. The 3 had radio controls in the steering wheel which was handy (
), had a better radio and more up-to-date interior but I found the red lighting to be extremely annoying and contrary to many a test, more difficult to see at night. The Sube felt more substantial though and gives better road feel, something specs will never tell you. Maybe the latter is more tire differences but the Sube had CdnTire issue Tiger Paws and the 3 had Michelin XMV Primacys! The 3's fuel economy was also similar as the Sube, but this is comparing a 2.0L w/4-spd auto vs the 2.5L w/5-spd stick. The 3 had a louder whine at highway speeds and the Sube just kept a subtle burble that the downpipe is known for. Between the two, the 6 year newer 3 has had more problems, big and small, than the Sube but that's just a sample of one between the two. In my experience, the Sube is the better vehicle.