Several factors will determine how your concert footage turn out. If you are shooting from the back of a concert hall, the GF10 poor AF may not matter at all because the long object distance will afford you sufficiently deep DOF to just focus manually once and forget about the it. The second factor is lighting. If the stage is very well-lit, both cameras will perform well.
However, if you are just at the foot of the stage and the lighting is insufficient, I will prefer to have the Fuji over the Lumix.