On first listen, I think both versions have their strengths and weaknesses. Overall I prefer Timbaland's production. Rhythmically it is much stronger than McClain's version, though I do feel he overdoes it a bit with the glass percussion. I think the intro and bridge, as well as the transitions back from the chorus to the verses, are nicer on the McClain version though. There are also some elements from McClain's string arrangement that I prefer, but I think he overemphasizes them and the arrangement sounds too forced around the vocal melody. Timbaland's is more subtle, and his version is driven a bit more by the rhythm guitars. What I like about McClain's version is that it is just MJ solo.
I do think both versions suffer a lot from the fact that MJ never properly recorded this track, for a number of reasons. 1. The fact that they did not have multitracks and the piano from the original ended up in these versions. Not only does it create a few awkward transitions whenever MJ's vocals cut in and out (and the piano is suddenly there too), but the piano part was played very straight. Rythmically it just does not gel with a full arrangement. That's also why JT's verse, where the piano is absent, sounds most natural musically. 2. Related to this, the fact that MJ sang his vocals to this piano part. MJ's timing was always impeccable and rhythmically strong. He did a nice job making things groove by the way he sang along to the piano on the demo, but because the piano is played very straight, his timing just sounds a bit dull and straight in this full arrangement. There's no doubt that he would have used different timing if he had recorded it to a drum track. This is why JT, who got to sing along to this full arrangement, sounds much more natural vocally on the track (though I still think MJ's voice is much stronger). 3. The fact that MJ did not record vocals to a click track. The vocals + piano go off beat a few times on both versions.
Overall, it is more or less what I expected to hear based on the album reviews and leaked demo. Fun song, but it is very noticeable that it is a polished up demo (mainly due to what I described above imo). Finally, I do like that they went for a retro production sound.