How to choose a PIC for a BLDC Motor Controller?
There are various PICs that have various level of motor control hardware built in.  At the lowest level you can use just basic PWM generators.  At the high end there are some intended for driving 3 half-bridges with programmable dead time and other logic.

Go to the Microchip site and look for the product selector.  You can easily get a list of all PICs with various combinations of features, like motor control PWM, some minimum amount of program space, certain size package, etc.