Got both of these in the last few days
Can't really say too much about them yet, the Khadas VIM2 is in theory a monster system, with an Octocore CPU and Mali 820 (not sure of the cores). It comes supplied with Android and I have to say its nippy as hell. I will try install Ubuntu, and give a report on its driver availability.
The VIM2 forums though are awful, very hard to find anything so it might be a while before I get to it.
The OrangePi Prime is a Allwinner H5, with a Mali450. no idea if the previous post notice about GPU drivers will apply to this 64bit system. Of course Debian as supplied had no drivers, and attempts to install them went a bit off, so I'm having a go at installing Ubuntu.
I will say though while using it the Debian install was quite light but noticeably nippy.
Ubuntu installed, it does have GL, but no GLES2 libs so I installed Mesa, however GLMark2-es2 installed and runs it, but as usual it appears to be software emulated as its painfully slow, with a pitiful score of 15, oh well I'll see if the Allwinner gpu fix works on it.