Our two Mini-ITX motherboards come with impressive feature sets, and they have nothing to fear from comparisons against mainstream ATX motherboards. Due to their compact footprints, Mini-ITX solutions won’t ever be seen with multiple expansion slots, extra memory sockets, or a plethora of add-in components. But all of the features you’d expect from a decent, modern PC are present: plentiful USB 2.0 connectivity, a handful of SATA ports, HD audio, gigabit Ethernet, support for more than 4 GB of memory, and accommodations for powerful processors and discrete graphics cards.
Zotac’s H55-ITX WiFi, outfitted with DVI, HDMI, S/PDIF, eSATA, and dual-band 802.11n, is geared for high-end PC and HTPC environments. Sapphire’s AM3DD785G is a bit cheaper, but also less feature-laden. You’ll have to live without WiFi, DVI, and digital audio.
Processor choice makes a huge difference in performance, power consumption, and power efficiency. Zotac's H55-ITX WiFi benefits from the very low idle power and high performance per clock of the Core i3/i5 processor family. Even the entry-level Core i3 does very well, beating all four AMD systems in many benchmarks, including idle power and power efficiency. AMD only shines in a few heavily-threaded workloads.
On the other hand, AMD has the more comprehensive low-power portfolio. Although no AMD setup was able to reduce system idle power to Intel's amazing 30 W levels, the low- and ultra-low voltage Athlon II X2 offerings restrain peak power consumption to numbers lower than Intel's. To get there, though, forget about performance. You're looking at basic office systems or industrial applications that won't need much cooling.
Lastly, consider cost and your expected applications. AMD still provides better bang for the buck with these Mini-ITX platforms. Intel costs more on average, but it will give you more performance per watt. The more you work with threaded applications, the easier it is to go with a quad-core AMD machine, as these are significantly cheaper than Intel’s lineup.