I'd say both are cool java application building tool. As what stated in Apache's Maven website, both tools are having different objectives. But what kind of objective is that? I think they are targeting to different kind of audiences and application scales.
I find Ant is good for those relatively small scale projects, eventhough it can perform well in large projects too. Writing ant target is an easy task if the writer knows what she wants to do, for example, she must know javac task for writing target to compile java classes. In Maven, they are using goal instead of target, although who don't know the existence of javac, she can write a working maven build script as long as she knows where are the java sources located.
The best thing I find is, we can integrate ant with maven easily, which the performance seens better than running ant itself.
