I'd probably reserve my opinion till I try both out. I have read arguments for both options in various audio forums and both seem to make sense in what it's trying to achieve in it's specific application. As for me, I may not go for a battery option right away...
Lately, I have installed Volumio v1.5 on my BBB. The sound is perceivably better than my previous installation of Debian+MPD albeit Volumio has same engine running behind the GUI. May be due to further tweaking of the OS from Volumio team. Whatever may be the reason, I am liking it!