There are indeed several valid comparisons between Witnesses and Mormons. As M. James Penton said so eloqently in the scholarly "Apocalypse Delayed", Joseph Smith and Charles Taze Russell were both "capable leaders" but "naive visionaries", while Brigham Young and Joseph Rutherford both "brought a sense of permanence to the movements they inherited". I can't agree more. Smith and Russell almost needed to die early in orger to not be faced with their doctrinal delusions, while Young and Rutherford could safely refine the words of their predecessors from a distance.
Well, to be fair, Joseph Smith came from New York State's "Ontario Country", which is still to this day rural in outlook and provincial in nature. In the 1820's, this was about as provincial as could they came.
Another thing about Mormons and Witnesses is that they were essentially borne out of the same spiritual awakening of the early 19th century. While Mormons were centered around Smith and his "discoveries", the Witnesses eventually sprang out of the millennialist movement which centered around William Miller at around the same time. While the Mormons have somewhat modernized their movement in recent years, the Witnesses are still stuck with the rigid Rutherford doctrines and Knorr 50's style morality.