Learning about the graphic limits of "devices" aka smartphones and tablets

My studio is a mobile game house, practically speaking our target platforms are Os and android devices.

I haven’t had to deal very much with device specific memory or performance issues, beyond the basic “make the textures/animations smaller” tasks.
I have the most basic grasp of shaders.

I’d like to educate myself better with the technical limitations of graphics on these devices.
It’s hard to google this without getting lots of useless cruft in the results.
I’s love to find some hard numbers on various device benchmarks
but I feel I also need some guidance to what the numbers might mean.

any resources I should look for?

I would personally play with a graphics debugger so you have access on common terms related to this topic. This way you can ask focused questions to your graphics programmers.
I am not well known with mobile devices, but this is how I learned about graphics with consoles.

A lot of it is the same anyway

I found this handy page at notebookcheck.net
http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html

Many specs, some of which I will need to research.