There are no definitive answer today.
All compilers do a good and decent job.
The difference between them are small difference in how they support language features.
see :
http://wiki.apache.org/stdcxx/C++0xCompilerSupport[
^]
On Windows : Visual Studio's compiler (or Intel's compiler)
On Linux (whatever flavour) : G++
On Mac : whatever is used in XCode (probably a version of G++, but objective-c is the main language on Mac).
M.