It depends a lot on your project. For large C++ projects, I've found scons and boost jam painfully slow for iterative builds. For smaller things they're possibly nice because they're expressive and pretty simple.

AFAIK, either make or vanilla jam is the fastest for C++, which is by far the most important thing to me, but that'll vary depending on your particular situation.

This is a bit old, but still accurate: http://www.gamesfromwithin.com/articles/0509/000100.html