Because she was there for The Doctor that needed her the most. The War Doctor trusted her, just like the Ninth Doctor trusted her. Rose will always be The Doctor's face and voice of reason AMEN! I love the Doctor and Rose!
As a response to 10 was holding it in so he could see all his companions again as himself and could do no longer when he reached the TARDIS. The build up of energy made it explode out of him whereas with 9 he just let it happen.