Millimeter-wave (mmWave) bands play a key role in 5G New Radio (5G-NR). They provide wider bandwidth and support much higher data rates. However, these bands also bring serious challenges. Signal propagation is more complex and affects system performance. This study fills an important gap. It compares two standard 3GPP channel models: Clustered Delay Line (CDL) and Tapped Delay Line (TDL). While many studies have looked at these models separately, few have compared them in realistic settings. We run simulations using CDL and TDL models defined by 3GPP. These models include both Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) conditions. We analyze key parameters like delay profile, delay spread, maximum Doppler shift, carrier frequency, and antenna setup. Performance is measured using Signal-to-Noise Ratio (SNR) and Block Error Rate (BLER). The results are clear. In NLOS, CDL models perform better than TDL. At 25 dB SNR, CDL-C achieves a BLER of 0.02%, compared to 0.3% for TDL-C. In LOS, CDL-D shows a BLER of 0.06%, while TDL-E reaches 6.495 \(\times \) 10 \(^{-5}\) %. These results highlight the need to choose the right channel model. Accurate modeling improves performance evaluation and network optimization. Finally, the study shows how advanced signal processing can reduce mmWave transmission issues.