My opinion on new version:

The boy was not near cute enough to extract maximum sympathy. As humor was uncharacteristically missing from this Hitchcock should have used a more whimsical child actor. Jerry Mathers comes to mind. With which some more humorous experiences could have been written.
The secondary, red herring, stories were not captivating enough, sometimes even to the point of cliche' and added to the unnecessary length that would need help filling even 90 minutes let alone 2 hours.
Using the use of music as the tool to locating the boy was clever but eliminated the suspense of the mother's marksmanship being required as in the first version. Which brings us to the anti-climatic ending.
The stair fall, though filmed with the usual Hitchcock panache, was much too quick and the nasty governess spy simply escapes. We should have been entertained with a gruesome demise of her.
I would conclude that the earlier version gains in pacing and suspense what the remake sacrifices with overlong dialogue and sumptuous cinematography.
Don't get me wrong. It is still a favorite of mine that I watch more often then the earlier version.