To make it clear we may have our personal preferences, but that is what they are….opinions. Some facts that we can put out there that may assist people new to the XU4 or rk3399 based board scene:
Odroid Game Station Turbo (Odroid)

Supported systems: xu4/xu3/c1
Website: Click Here

 This is built on top of the X11 environment making it very robust for features. You can not only use your XU4 as a “game” machine, but also as a desktop and has a great Kodi build. The dev Meveric is very responsive to questions and has put a great deal of time into the build. This has been a longstanding theme as he has been developing and supporting the build since around 2013. His build can be found and discussed on the Odroid forum.
Recalbox (Odroid, Rock64 Pro TBD)
Supported systems: xu4/xu3, Rock64 Pro
Website: Click Here
Recalbox is based on the GNU/Linux Operating System. It contains thousands of different types of open source software; from tiny utilities to the massive EmulationStation Frontend. It also has media integration with Kodi. It is a great choice for those wanting to just burn the image, add their content and go. The customization piece is not as easy as RetroPie however if you invest the time into learning how to code for it then there is some customization you can perform. RCB has a forum community to discuss the disto.
Batocera (Odroid)

Supported systems: xu4/xu3
Website: Click Here

Built off the bones of Recalbox per our understanding it is a fork of RCB. It is still similar to RCB as in it is more designed to be burn, plug-n-play and go. Customization is once again like RCB not as friendly as RetroPie however it has an active dev that takes requests for new features and functionality as well as a community forum.
Lakka (Odroid)

Supported systems: c1/c2/xu4/xu3
Website: Click Here

Lakka is a lightweight Linux distribution that transforms a small computer into a full blown retrogaming console.It has an interface that lends highly to the default RetroArch UI and is similar to the Sony PS UI of old. The dev team has little experiences with it as of yet.
TheRA (Odroid, Rock64 Pro TBD)

Supported systems: c2/xu4/xu3
Website: Click Here

RetroPie is by far the largest retrogaming community out there and we have leveraged it to create our own formal and official fork known as TheRA. TheRA allows you to turn your ODroid XU4 and soon to be rk3399 based boards like the Pine Rock64 Pro into a retro-gaming machine. It builds upon Debian based minimal distros , EmulationStation, RetroArch and many other projects to enable you to play your favourite Arcade, home-console, and classic PC games with the minimum set-up. For power users it also provides a large variety of configuration tools to customize the system as you want. It by far and away is the most robust for customization to include repositories for themes, launching screens, splashscreens, etc. Since it runs off of standard Linux and web based standards/languages it has built a very large community globally.
KODI (Odroid)

Supported systems: multiple
Website: Click Here

Kodi wants to entertain you. Kodi spawned from the love of media. It is an entertainment hub that brings all your digital media together into a beautiful and user friendly package. It is 100% free and open source, very customisable and runs on a wide variety of devices. It is supported by a dedicated team of volunteers and a huge community. Kodi is traditionally aimed at consuming media such as music, TV, and movies. Kodi can have high customization with various skins and plugins available.