Yes I am not taking about shoot thru window, but heli with doors taken out.
Not necessary to have gyro all the time. When shooting at low light situation yes gyro would be useful. Gyro is rather heavy and I usually use it with a improvised rig ie using bungee cord.
Here's a pic of "Nikon" with a gyro
To the TS sorry for the OT.
Back to the topic.
Between the 17-55 and 24-70 there is a big difference as highlighted by the many posting here. But one must bear in mind the different uses for each of the lenses.
I still keep my 17-55mm DX lens cos it is coupled with my D200 as a back-up. I find the 24-70 on the D200 lacking at the wide side.