I've got the Shark model above and couldnt be happier. Not sure I agree with the above poster regarding allergens as the Shark model states:
"Anti-Allergen Complete Seal Technology + a HEPA filter. Traps 99.9% of dust and allergens inside the vacuum"
Shark model is great value, though its largely plastic, but in comparing that aspect to the much more expensive Dyson, its all plastic these days, so cant yet comment on lifespan, but I'm 3 years into the shark and zero problems.
And btw, I too have a 2000+ ft2 home, and a heavy shedding dog, my kids also have allergies. I am AMAZED at how effective the shark picks up all that dog hair.