Although the just announced Mac minis don't seem to be out in the wild yet, the geekbench developers have written an interesting article estimating it's likely performance:
http://www.primatelabs.com/blog/2014/10/estimating-mac-mini-performance/
Although single-core performance is slightly improved over the 2012 model, as many predicted multi-core performance takes a massive hit owing to the lack of a quad-core configuration in the new lineup.
There's no discussion of what difference Intel Iris (in the mid and top level 2014 model) will have over the 2012 model's Intel HD 4000 thou