I think best supported device is nexus 4. It's much more stable then my Nexus 5 and Aliendalvik with gapps (i made it) works without problems. It does not work on OPX. So the best device for SFOS (not looking to hardware) is nexus 4 IMHO. I Still would not buy OPX over Nexus 5. I like Nexus series. They are created for developing.