Someone explain the difference in the Olevia models to me please

As far as PQ goes what is the difference between the 3-series, 5-series, and 7-series, other than the fact that the 7-series is 1080p. Do they all display an equally good (or bad depending on your opinion of Olevia) picture or do the 5's look better than the 3's and likewise for the 7's and 5's? Or do they all look just as good and the more expensive models simply have more inputs/options or something?