1. Isolation Voltage: The TLP187 features a significantly higher isolation voltage of 3750 Vrms compared to the TLP127's 2500 Vrms. This allows the TLP187 to withstand higher transient isolation voltages, providing a stronger electrical safety barrier. It is better suited for applications with stricter safety requirements (e.g., reinforced insulation) or those with a higher risk of voltage surges. 2. Package / Thermal Performance: The TLP187 utilizes a standard 6-SOIC package. Compared to the TLP127's 6-MFSOP (a smaller form factor), the SOIC package offers a larger die-attach area and a thicker lead frame. This translates to superior long-term operational reliability. Particularly when driving loads close to 150mA, the TLP187 maintains a lower junction temperature, thereby extending its operational lifespan. 3. Operating Temperature: The TLP187 offers a superior maximum junction/operating temperature range of -55°C to 110°C, compared to the TLP127's range of -55°C to 100°C. This improvement is directly linked to its enhanced package thermal characteristics, enabling stable operation in more demanding ambient temperature environments. 4. Forward Voltage: The TLP187 has a typical Vf of 1.25V, slightly higher than the TLP127's 1.15V. Consequently, for the same input current, the TLP187 requires a marginally higher drive voltage or dissipates slightly more power. However, this difference is minimal and can generally be neglected in circuit design.