HTML5test.com doesn't test performance at all, as far as I know. So a device could score higher but be too slow to use.
Does anyone have a PS Vita? Have they tried to test performance? This is my standard performance test now since it gives a pretty representative score: http://www.scirra.com/labs/sbperf/
I just got a PS Vita today and haven't even unpacked it. I'll run some tests and get back to you. I also have a Nintendo 3DS. It would be really great to run HTML5 games on either or both of them!
In particular the 3DS is really picking up and having a lot of cool downloadable games!