One of the punchiest ARM options is the quad-core RK3188. It has the least punchy GPU in the class, a clock-increased (by 25%) Mali400. However, this is the ARM-coupled GPU with the most functional OSS driver. It is already possible to boot Linux on RK3188 directly, and play Quake3, with an OSS driver. OHI, there is now an installer. However, it does not appear that the installer includes recovery. Hmm, reading further, it does not include the accelerated video driver or working bluetooth either, so I guess I'll stick with Finless for now on my MK908. I want to run Linux for a variety of reasons, not least PS3 BD Remote support.
With that said, if the MIPS tools are better, I'd still rather have MIPS for a Linux box. It's not that interesting for Android though, since the majority of the Android world is on ARM.
Also, it's possibly notable that nVidia has stated repeatedly that Tegra's GPU isn't encumbered by agreements with other corporations as their desktop GPUs are, and that they will continue to release increased amounts of driver source code for that platform. I'm not holding my breath, of course.