Actually, two of those are haswell devices with considerably faster graphics, and I think all of them are about 1/3rd the physical volume of the mini.
The i5-4250 is as good or better than the current i7 mini, particularly if you're in need of something better than the HD4000 graphics.
There's also the gigabyte brix lineup, which are similar and include an i7-4500. There's supposed to be a brix-ii with iris pro on the way, but there's no firm release date.
You can get the i7-3770 zotac box on amazon, and that's definitely faster than the i7 mini since it's using the desktop part and not the mobile part.
Yes, you can't run MacOS "legally", but all of these are hackintosh targets.
That being said, the mini is one of the few apple products that make some financial sense....if you want something that small, they're very competitive.
The iMac is pretty overpriced for what you're getting, and the Mac Pro is stupidly priced for the average consumer.