I would say that it depends on the loss: for the MSE loss it is probably the same because mse(a,b) = mse(b,a), as you are doing the square of the error. The same holds for the mae criterion, because you are taking the absolute value. But be careful: this does not hold for measures such as the kullback leibler divergence, for which kll(a,b) != kll(b,a).