personally I'd stick with the 6cyl.. current ones are pretty decent.
4cyl wouldn't have the torque needed for a heavy family car imo
you'd be wrong, eco boost is making 353nm@2000rpm, it is more torque than the 3.6l commodore V6, (albeit 3nm) so call it the same torque as a large family car that people buy, and in a package that weights less, pretty sure hills wont matter (which in case you missed it, was the point of the ad!)
and using the ADR fuel sticker, it does all this sipping less fuel than a mazda 3
one thing is that the rev's are pretty line ball with the big lazy 6, it (the ecoboost) doesn't rev hard to make it's power, it really is worth driving it before making comments like "4cyl wouldn't have the torque needed for a heavy family car imo"