My sigma 120-400 has 3 settings for IS -full, panning and off.
Off is reccomended for tripod use, full for handheld and panning speaks for itself.
I used to have an olympus E3 with 50 -200 f2.8.
It could not cope with aircraft very well and the autofocus hunted like a sonofabitch, and as for low ISO noise!
It was like a big 'join the dots' puzzle.
Choose your camera wisely as it expensive to change your system.
If the camera you need costs a little more, then save some more for it.