WAP7 is a cloned version of WAG9 and its TE output is satisfactory only up to a maximum speed of 140 km/h. Beyond that, it's too low to sustain. WAP5 always has the upper hand when it comes to higher speed ranges.
Reason is : WAP5 is a high horsepower Bo-Bo locomotive. Its high HP output comes from just 4 traction motors (unlike 6 in WAP7). Apart from that, it has several advanced features which support smooth and efficient high speed operations. As a result, WAP5 will be the obvious choice for Gatimaan, Bhopal Shatabdi, TALGO and upcoming high speed trains.