WRDE-LD is omni-directional, and serves Southern Delaware, Ocean City, MD, and Wildwood/Cape May NJ. It replaces WMGM-TV as the affiliate there, but doesn't overlap with WCAU. The overlap of WMGM-TV with WCAU was about to increase significantly (with the addition of WMGM-LD), so I'm sure Comcast/NBC views WRDE-LD as a better match for the network.
One difference in terms of cable coverage: Rehoboth Beach is part of the Salisbury, MD market and not Philadelphia/Wilmington, like WMGM-TV is. At least I'd think NBC owned and operated WCAU-TV has exercised their right to be the only NBC affiliate in the Philadelphia/Wilmington market.
It would still be nice to see the Philly and Baltimore channels carried on cable in Rehoboth and parts of the Eastern Shore. As many visitors and vacationers come from these areas. And I think they may have even used to carry a DC channel possibly.