Let's assume that all charges flowing in both wires are either all positive or all negative. From the frame of reference of an individual charge in either wire, it would appear as if the position of all charges were static and that this could be treated as an electrostatics problem. By treating it as an electrostatics problem, though, I would expect the wires to repel one another.
If, on the other hand, we were to assume the frame of reference of either wire and were to solve for the net force due to the currents in each by treating it as a magnetostatics problem, it seems that the solution indicates that the wires would be attracted to one another.
Where is the error in this logic?