what is the best compiler for PIC microcontrollers?

First of all to be good in Microcontrollers programming you should learn something very important ;that thing is the key .....

The key is the data sheet of the device ....

In my opinion reading datasheet carefully is 90% of work ....

Also when i started learning microcontroller i learned assembly ;in my case i learned PIC family of microcontrollers....the amazing part of PIC is the smallest number of instructions; it is RISC processor which means (reduced instructions set computer)...For example the PIC16FXX family had only 32 instructions and the PIC18FXX had only 75 instructions ....it is amazing only 32 instructions and you can excute any intruction from them ......

My learning process start with :

1. writing Assembly using MPLAP

2. use PICBasic Pro compiler

3. Finally mikroC V6.2

MikroC is very good but don't miss the golden rule of learning "The data sheet"