When comparing ODROID-W vs Onion - Omega 2, the Slant community recommends Onion - Omega 2 for most people. In the question“What are the best single-board computers?” Onion - Omega 2 is ranked 44th while ODROID-W is ranked 64th.
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Pros
Pro Software compatible with the Raspberry Pi
ODROID-W is compatible with the Raspberry Pi at least as far as software goes. It can run any software built for the Pi.
Pro Amazing heat dissipation
The ODROID-W has some great heat dissipation. From studying the heat of the heatsink, the maximum temperature registered was 37 degrees Celsius, and that was registered when the board was doing a lot of unpacking through apt-get. Normally the temperature is even lower than that.
Pro Can fit most Pi cases
Since it's built to emulate the Raspberry Pi, it's roughly the same shape albeit a bit smaller. But even then it should be able to fit most Raspberry Pi cases.
Pro It's tiny
Pro It has lots of shields available, including Arduino shield
Cons
Con Obsolete
Don't fall in love, this model is no longer available.
Con No on-board Ethernet
The ODROID-W has no on-board Ethernet port available, however this can be fixed by using a docking board which has an Ethernet jack.
Con Needs a multi-USB hub
Since it only has a USB host connector available for a full-sized port, you most certainly will need a multi-USB hub to connect more than one external devices to the board.
Con Not breadboard compatible
The board does not have the standard 2.54 mm pin spacing.
Con Support issues
There have been long-lasting periods were everything grew stale, even when it was about fixing security issues etc. have given up on checking since it was frustrating.
Con Expensive
It has less than 256MB of RAM.