I'll be speaking of the old (current rooms that haven't been redone yet), standard rooms in this reply. I've stayed in a standard room in the North Garden Wing, but have not stayed in a tower room.
The standard rooms in both the tower and garden wings are the same size and have the same decor. The only difference is that in the garden wing rooms, the main part of the bathroom contains two sinks and the toilet is located in a separate room that contains a countertop (no sink) and in the tower room, the main part of the bathroom contains one sink and the toilet room contains the other sink.
Also, the tower rooms have balconies, the garden rooms do not, but the garden rooms on the first floor have small patios that contain two chairs and a small table.