Hi,
the new Westin Berlin is now a really good Westin Hotel. There is nothing wrong and if you've never stayed there before you will be happy with your choice.
The Westin Grand is the former Grand Hotel of the GDR. It was renovated for the last time at '87. And it was something special. You've loved it or you hated it, now it's a just Westin (without a lounge).
The Hilton in Berlin is also a great Hotel with a great view if you're in the one of the right rooms.