Although CNET did not review the Sony KDL-HX729 series, we did review the similar KDL-NX720.
Comparing the two on Sony's Web site, the HX729 has Sony's "Deep Black Panel" while the NX720 has the "OptiContrast Panel." We can't be sure how this difference affects picture quality, especially in bright rooms, but we suspect the two will have similar black-level performance since both use Sony's Dynamic Edge LED backlight (more info).
The HX729 has a 240Hz refresh rate, compared with the NX720's 120Hz. We don't expect this difference to have a major impact on 2D picture quality (more info), although it might improve the HX729's 3D performance in regard to crosstalk. The HX729 also gets Sony's X-Reality Pro video processing engine while the NX720 does not; in our HX929 review the Pro engine didn't seem to make much of a difference, especially with HD sources.
The NX720 has Sony's Monolithic design, which we really liked, as we discussed in the review. The HX729 has a more traditional design, similar to that of the EX720 but with a darker bezel.
The largest member of the HX729 series is 65 inches, while the NX720 tops out at 60 inches.
As far as we can tell there are no other major differences between the two series, and we expect they'll have similar picture quality. For more information, check out our full review of the Sony KDL-NX720 series.