Marc Edwards of Bjango has put together a nerd-ily in-depth look at how different screen sizes -- original vs. Retina display on iOS, new vs. old Android displays, and Windows 8 Metro standards -- challenge designers who strive for pixel perfection in their work.
As you can see, scaling to any size other than exactly double is detrimental to the accuracy of how your original design is represented on screen. The asset scales of 140% and 180% required for Windows 8 Metro hit their target less than 25% of the time. Android’s 150% scale lands on a neat pixel boundary half the time.
I've discussed the tradeoffs before when rumors claimed Apple was going to release an "HD" but not 2x Retina display iPad 2. Marc takes it far further however, with charts, spreadsheets, and examples of what exactly all these different screen sizes do to the integrity of the design.
At the end of the day, would someone moving up from a feature phone to an Android or Windows 8 phone notice or care about blurry pixel grids? Many probably won't. I still think Apple does, however, which is why we'll either get the same size screen on an iPad 3, or a Retina display, and nothing in between.
Hit the link below for Marc's full rundown, and stay tuned for the next episode of the Iterate podcast where he goes over his findings.