CCS C and High-Tech C are in my opinion the best, but you will pay for them, both have student versions with limitations. I use both each have strengths and weaknesses. Both companies realise this and you can now produce Object file for inclusion in the other, a bit like DLL/lib files.
Download MPLAB C18 ot C30 compiler student version.
It will work like a full version for 60 days.
You can check its performance within 60 days.
If it is good for you then order full version.