Windows Phone is an OS that performs well on nearly any hardware. From the low-end iterations like the Lumia 520/521 to the top of the line Lumia 930, Windows Phone has proven to scale well across many different screen sizes and hardware.
Of course, this was by design and after spending a few days with Microsoft and their Windows Phone staff at BUILD, a little bit of light was thrown onto their process which highlights why Windows Phone works so well on low-end devices.
When developing the Windows Phone OS, developers are required to use low-end hardware and we don't mean that they have it on a test-bench and occasionally use the devices for testing. Nope, the devs must use the low-end devices as their phone to make sure that Windows Phone works perfectly on the low-end hardware at all times. While higher-end hardware is tested, for daily use devices, it's low end hardware or bust.
The logic is quite obvious, it's easier to scale-up in performance than it is to do the reverse, and it's one of the reasons why Windows Phone will always work well on all types of devices. It's also important for Microsoft to build for low end and optimize for high end so that the entry level devices offer an experience that Microsoft can be proud of, unlike some Android devices in the early days of the platform, that had less than optimal experiences with entry level hardware.
More so, seeing that Windows Phone is selling the most units in the low-cost market and the new 630 and 635 that were recently announced, Microsoft and Nokia are continuing to push the low end of the spectrum to help take market share in the lucrative smartphone segment.
When you start to look forward with Windows Phone 8.1 and the new features it will bring to the platform, it's good to know that Microsoft is truly keeping all devices in mind when it builds out its feature-set and does not try to differentiate between high and low-end hardware.