Over the years there has been a "convergence" of turboprops and jet engines as bypass ratios have got bigger and propulsive efficiencies are more matched. However, turbofans of high bypass ratio ( these days up to 10:1) will always be more effective/efficient at higher speeds due to the fan duct itself, reducing "tip losses" and concentrating the airflow to give an optimum duct pressure ratio of 1.6 and therefore a more useful acceleration.