Difference Between HiTech C and Microchip C 18 Compiler and USB Operation

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Hello!!! Everyone
I want to use the USB .. thats why Choose PIC18F4550 Micro-Controller..

and thats why I have downloaded the Microchip Application Frameworks...

Formerly i am using Hi-Tech C Compiler..
But the programs given in Microchip Application Frameworks are for Microchip C18..

So i downloaded the C18 Compiler and wants to use it..
and I will do so...

But i want to know which is best compiler and are there any inbuilt functions available in Microchip C18 as in Hitech-C

some function like __delay_ms ; __delay_us etc etc..

and I have read some programs related to USB from Microchip Application Framework but they are not so simple to understand
for a beginner like me..
can any one suggest me how to do so..
I am having the basic knowledge of USB and wants to make some simple device based on HID Class...

Can anyone tell me how to manipulate the Microchip Application Framework code to make my own code..

Thanks in Advance