IMO, go for the Everest. More power (156 hp and 380 Nm for Everest, 146 hp and 315 Nm for the Alterra), more gears (both are auto 'boxes, but the Everest has 5 gears, while the Alterra has to make do with 4), an LSD for the Everest, and most of all, smaller dimensions (but strangely, heavier curb weight) also for the Everest.
Space-wise, one may not believe it, but they have almost the same, if not bigger for the Everest, interior space (despite the Alterra being longer than the Everest). Except if you intend to use all three rows (both the Alterra and the Everest still don't have at the least headrests for the 3rd row). NVH levels are, for me, just right. (i.e. both are comfortable enough for long travels, except again if one is on the 3rd row.)
Some drawbacks? The Everest has fewer amenities than the Alterra (the Alterra has a 5.1 surround sound system, factory installed), and the twist-type parking brake may not be appreciated well, especially that most of us are weaned to floor-mounted e-brake levers. Another is that the gear shifter for the Everest may be confusing to use at first (since the gear indicators on the shifter are located on the passenger side of the shifter.)
Fuel consumption? Well, the least I know are the manufacturer's claims: 8.64 km/L for the Alterra 3.0L, 10.87 km/L for the Everest 3.0L.
That's all I can say for now. It's all up to you to choose.
Hope that helps.