Windows 7 64Bit, GTX 770
40dbf2f / 5bd8ac9 (2.79 stable)
When an object is in a group, if it is the scene's active object, performance will drop.
The object can have a group and be selected without dropping fps but only if it's not in a group.
Here is a scene with two empties, and a monkey with some modifiers (to drop fps to see it)