Short Answer
Maven. Maven have some small advantages over Gradle but you drive good with Gradle.
TLDR
Gradle Pro
It works, mostly. New features appearing earlier. Great driver for Maven features.
Gradle Con
Some times it doesn't work.
Semantic changes.
Log handling is not intuitive.
Build file structure is not so clear like in Maven.
The build.gradle file looks like a mess if some newbie try to adapt, improve, re-structure, optimize the build process. The scripting ability is a clear con. If you think you have to adapt the build process in the build.gradle, think twice maybe your process is the problem.
Maven Pro
Higher stability and fixed well designed build process.
Maven Con
XML is for the upcoming devs a new things to learn. XML is little bit bloating.
