I have Arduino IDE 1.6.11 and 1.6.5 installed.
Flashing grbl with 1.6.5 shows the following file size: Sketch uses 29,038 bytes (90%) of program storage space.
while using 1.6.11 has: Sketch uses 30,852 bytes (95%) of program storage space.
It definitely seems like newer versions of the arduino ide are using up more of the onboard storage.