Generally not really any better or worse. The electric bits added in a PHEV is relatively ancient, simple and reliable tech - ~5 to 20kwh battery plus a small electric motor added to the end of the existing transmission in most cases. Electric motors in vehicles generally have little to no maintenance requirements and just last the lifespan of the vehicle - the stator/rotor never "touch" so there isn't anything that "wears" anything like as much as in a combustion engine and no complex lubrication challenges. The battery will wear over time, but again generally lasts most to all of the lifespan of the vehicle.
In some cases reliability actually improves, as the extremely reliable electric motor can replace things such as reverse gear and the starter motor, reducing complexity of the ICE system and transmission. The only parts being serviced that you pay for continue to be the gas bits exactly as before.
In some cases reliability actually improves, as the extremely reliable electric motor can replace things such as reverse gear and the starter motor, reducing complexity of the ICE system and transmission. The only parts being serviced that you pay for continue to be the gas bits exactly as before.