I was in the same situation about 4 month ago, and I wasn't familiar with Grails, but I want to have a platform to develop our website very fast and I think our project is as big as yours, we started to work with spring and start using spring roo for mvc but as time goes by we find out that spring will not satisfy our need, and roo is not what we want so we switch to Grails and I found Grails one of the best web frameworks that I ever worked with. here is one of the question that was in my mind about spring roo.
All in all as a satisfied customer of Grails, strongly suggest Grails.
(In my opinion, Grails and AngularJs are the prefect match.)