In terms of what either of them would do as AG, it doesn't make a difference. What these RINOs do not get is Holder leaving office and Lynch being nominated is a opportunity. Republicans could put the pressure on Lynch to the point that she gives up. Concurrently, they should be attacking Holder. This can continue with each nominee thrown at the Senate, since I am sure Obama will nominated only like minded people. The goal is to expose Democrats for what they really are while promoting conservative principles. Any opportunity for an argument is good. It will reflect poorly on Obama and more generally all Democrats.
The problem with Republicans is that they are impotent and too few actually have any principles.
This only works with those who are paying attention. To all the rest it eventually reaches the point of obstruction. You have to know your audience.