The main differences between the two techniques is that the "white noise" technique is faster, but the accuracy of your results is dependent upon the accuracy of the white noise generator. The sweep technique is slower, but you can compensate in nonlinearities of the signal generator output. Also with the sweep method you might not need an arb, a good sinewave generator might work.
The answer of which to use depends on how fast the test needs to run, and the accuracy you need.
Mike...