Think as well as cabin options, about your dining options....
Princess offer an "anytime dining" option which may be more flexible for you.
I've been on Vision OTS, and Golden & Star Princess (sister ships to Grand) and must admit that while the RCI ships are more attractive visually, I prefer the quality of the Princess product.
The main dining room on the Vision class ships is much more cramped than Golden Princess.
However, Vision's buffet restaurant is nicer than Grand Princess. But Grand Princess scores for the 12 year old with a pizza counter and a burger/hot dog counter right by the main pool. And there's a teen area on the top deck, with hot tub & DJ. And a massive arcade.
Also, count the swimming pools on both ships.... a 12 year old on Vision class has one main pool, with the indoor solarium pool being adults only. On Golden Princess there are more pools to choose from.