DMD has the fastest compilation times and gets new features right away. LDC will produce faster code for the times that you need to maximum performance. GDC takes longer to add new features than either DMD or LDC, but it produces fast code.
In my experience, gdc has produced faster code than ldc for my problems. This is subjective, so please don't ask me to produce benchmarks. I just remember gdc outperformed ldc in some cases, that's all.
