Compiling Groovy code is typically slower than compiling Java code, but in 14.1 we took a swing at speeding it up.
First, we're now supporting Groovy-Eclipse compiler that handles Java and Groovy simultaneously, which brings a noticeable performance gain. So, if you're compiling your projects in Eclipse, you might want to give this new integration a try. Just go to the Java Compiler settings, select Groovy-Eclipse, and point to the groovy-eclipse-batch.jar. Remember that is should be the same version as your Groovy distribution.