The GPU isn't the problem. It's the fact that Allwinner still hasn't created an Android OMX stack for their hwaccel video codecs.
People don't understand that the ARM SoC world is different than the desktop world - in the desktop world, EVERYTHING graphics-related is on the GPU, and it's all blobbed up.
In the ARM SoC world, the graphics subsystem is split up significantly, with a lot of mix-and-match opportunities.
For example, Mali 400MP GPUs are found in a wide variety of SoCs - Samsung Exynos4, Allwinner, Amlogic chips, Rockchip RK3066, some MediaTek chips, and I think a few others. People say, "when will there be hwaccel on Mali" - the answer is NEVER. This is because hwaccel video decoding is done by separate components in the SoC. In the case of Samsung Exynos, it's Samsung's MFC. In the case of Qualcomm, it's "vidc". In the case of Allwinner, it's CedarX. Amlogic's is just "amplayer" or something like that. FYI, at least the kernel interfaces (albeit not the firmware) for MFC and vidc are open-source, as are OMX stacks for both of those implementations.
You can also see other interesting pairings too - for example, Samsung's MFC engine is very similar between Exynos3 and Exynos4, despite Exynos3 having a PowerVR GPU, and Exynos4 having Mali 400MP.
Samsung's MFC has "good enough" OMX support to do XBMC on Exynos3, 4, and 5.
Allwinner simply has NO OMX decoding solution for Android using CedarX, only their special proprietary player.
Same for Amlogic's amplayer - the only reason XBMC works with Amlogic chips is because XBMC had "special" nonstandard playback support added.
The end result is a lot of people.