When I started university in the mid-1970s we worked on both analog and digital computers. The main digital computer wa sin its own building -- we created out programs on punched cards and/or paper tapes. My mind boggles when I think that each of the SBCs discussed in this column could probably out-compute that room-sized beast...
Turns out that Hardkernel is getting set to release in September a new board, the XU, which has a big.LITTLE architecture (Exynos5 Octa Cortex™-A15 1.6Ghz quad core and Cortex™-A7 quad core CPUs). Thus, while the U2 has more than enough power to serve as my everyday Linux system, I have my preorder in for an XU Board. One can never have enough speed!
Nice summary of these interesting boards. I have been using an Odroid board for a while, and spotted a few small mistakes in your description. First, the Odroid pictured is the X model, while the model described is the X2. Unfortunately, the X2 sells for $135, not the $89 listed. The Odroid U2, the version I have been using, does sell for $89 and differs substantially from the X2 only in that it has two (instead of six) USB ports. I have gotten around this limitation without issue by using a small powered USB hub.
The Odroid U2 serves as my main Linux machine (Ubuntu 13.04, no overclocking, classic gnome desktop, 1920x1200 resolution using the board's HDMI port). While I do not set out to stress the system (and have not done any benchmarking), I have yet to run any application that showed any noticeable lag. Indeed, I recently installed the Accellera (OSCI) SystemC Simulator on this system for fun, and the performance is reasonable.
I also run Android (Jelly Bean 4.1.2) from an micro SD card, primarily to use XBMC, which runs quite well on this machine under Android (but not yet under Ubuntu)
The Odroid user community (accessible on the Hardkernel site), while not as extensive as that of the Raspberry Pi, is active and helpful.
I have previously owned a Raspberry Pi and a Hackberry A10, and found that both were too underpowered for everyday general use.