I think the better question is... Is it Beane or Mc D... I think McD has total control over the coaches... seems satisfied and made no changes... to me it is not possible to look that the performance of these two and not believe that they our completely out gunned... Thus for any coaching issue as well as on field performance like play calling, execution and just simple blocking and tackling as well as game planning... by virtue of his initial hiring of this staff and commitment to them I blame McD...
The personnel to me is on Beane... too many wasted draft picks, failure to scout and identify top round players to make a difference, not effectively obtaining Josh the appropriate weapons to allow hm to succeed, too many draft misses to include who was drafted as well as who was available and could have been drafted, too many contracts paying non or little difference making players big money cash strapping us, and kicking the salary cap down the road hurting our future for poor to moderate current return...
In the end every team has an Elam or a Coleman... I get it... but outside of Allen and Cook who has he drafted that is a star... a game wrecker or a player other teams game plan around.... He has done well with the O Line I will give him that... although this is hard to say after they almost got Josh killed yesterday...
At this point Beane has tried to fix the flat 5 times its time for a new tire... while the engine (Josh) on this car is still in good shape and capable... this may mean the car is on the lift for a while but it will run much better with the proper fix.
That proper fix to me is getting in a new GM to fix this mess, draft and scout appropriately and build a team that can win a Super Bowl as the current team cannot. This means taking a step back and clearing some of the deck... This also involves likely a new coach and coaching staff...
So in short my answer is Both. And it isnt going to get better over night.