To systematically evaluate the accuracy of GPS LNAV and CNAV broadcast ephemerides and verify their performance in real-time applications, this study conducted a year-long accuracy assessment for 2024 based on GNSS broadcast and precise ephemerides, complemented by validation through real-time orbit determination (RTOD) experiments using LEO satellites. Broadcast and precise ephemerides from 2024 were used to perform statistical analyses of ephemeris accuracy across different satellite blocks and navigation message types. In addition, reduced-dynamic RTOD experiments were carried out using onboard GPS observations from the GRACE-FO C satellite to assess the impact of different broadcast ephemerides on orbit accuracy. The results show that the accuracy of broadcast ephemerides varies significantly among satellite blocks, with BLOCK IIIA performing the best and BLOCK IIF performing the worst. After the clock source switch on G08 and G10 in 2024, the constellation-averaged SISRE for LNAV and CNAV broadcast ephemerides reached 25.5 cm and 23.8 cm, respectively, representing a substantial improvement compared to the LNAV SISRE of 37.0 cm in 2021. The LEO RTOD experiments further demonstrated that, compared to LNAV, CNAV provides improved accuracy in the along-track, cross-track, radial, and 3D directions, with a maximum reduction in 3D orbit error of 0.8 cm and an average improvement of about 3.2%, thereby confirming the advantage of CNAV in real-time applications. Overall, both the ephemeris accuracy statistics and LEO RTOD results consistently indicate that CNAV broadcast ephemerides outperform LNAV. With the gradual retirement of BLOCK IIR satellites and the continued deployment of BLOCK IIIA satellites, navigation, positioning, and timing services based on CNAV broadcast ephemerides are expected to achieve even higher accuracy, further enhancing their value for real-time positioning and scientific applications.