Listen, there is not a proportionate number of reviews of both players...the 5000 is simply more popular (as evidenced by this forum) for better or for worse, so there will naturally be more complaints and more reports in the wild on the 5000.
Here's a quick comparison in # of reviews:
Circuit City: 37 vs. 18
Crutchfield: 18 vs 4
Amazon: 40 vs 20
Maybe this implies there *were* more problems (most reviews were written well before firmware revision 1.3) or maybe the 5000 simply saw a healthier sales rate due to brand recognition and/or initial positive press releases. It's hard to say but one also can't say with any conclusive proof that the 5000 is more incompatible with HD DVD with a straight face.