Questions like should I use X or Y depends always on your experience with these tools and the requirements.
The best tool/framework is worth nothing if you do not know how to use it and if you have no other requirements than "I want to build an app", I would suggest to use the tool you feel best with.
The pros and cons of GWT are explaind quite often. I think its not neccessary to be repetitive.
Greetings,
Peter
