Not so fast my friend, you didn't read close enough

... a
dual-core 2011 Mini 2.5/Radeon-6630m/1333MHz-bus/256GPU-RAM beat a
quad-core 2012 2.6/HD4000/1600Mhz-bus/768GPU-vRAM in a Cinebench Open GL test. So basically the Radeon-6630m is giving up a delta of two cpu cores, 0.1 Mhz cpu speed, 267Mhz bus speed, and 512MB-vRAM and is still beating the HD4000 by 6%! That hardly means the 6630m is only 6% faster, it's only 6% faster on the 2011 platform in the Cinebench OpenGL test.
In fact, notebookcheck.net shows the 6630m is 63% faster than the HD4000 in the 3Dmark11 test (999.8 vs 613.6) which is probably a better indication of their relative speeds on similar platforms.
6630m>
http://www.notebookcheck.net/AMD-Radeon-HD-6630M.43963.0.html
HD4000>
http://www.notebookcheck.net/Intel-HD-Graphics-4000.69168.0.html
The 2012 Mini 2.6 is a beautiful machine, but its Achilles heel is the pitiful HD4000, which is way underpowered for this class of cpu. Obviously, Apple did this by design so as to not undercut iMac and MB sales! Too bad!