Types of Compilers Supported in S60 v9.x SDKs.

1. WINSCW : Used to build an S60 application for the emulator. A WINSCW compiler is delivered with the Carbide products.
2. GCCE : A free GNU C Compiler (GCC) Embedded Application Binary Interface (EABI). The compiler is delivered with the S60 SDK and can be used for compiling S60 applications for mobile devices.
3. ARMV5 : ARMV5 builds are created with ARM Real View Compilation Tools (RVCT, version 2.2). ARM Real View Compilation Tools are usually used for performance reasons, when compiling S60 applications for mobile devices.

Note:
1. When compiling for Device code compiled with ARMV5 is usually faster and small size then GCCE.
2. If you want to improve GCCE performance or want to upgrade to newer version then you can get it from http://www.codesourcery.com/gnu_toolchains/arm
3. Abouve recommendations are not must have but what i use, so you can differ with it.