Locality is important, in fact it's the largest factor in determining speed of a hotkey's access.. "distance from home-row"[0] is a measurement that is consistently touted when referring to vim in particular.
Control+[ is significantly faster because your hands move independently. However I'm just now remembering that I always remapped my capslock to be an additional control, so it isn't necessarily universal that control is "as fast" since my "control" is actually on the homerow.. which is unusual.
As it happens, though I was wrong earlier and was confusing ^c and ^[
from `:h i_CTRL-C`
> CTRL-C: Quit insert mode, go back to Normal mode. Do not check for abbreviations. Does not trigger the InsertLeave autocommand event.
^[ is interpreted exactly the same as ESC; vim can't see a difference. (you can see this under `:h keycode` )
[0]: https://books.google.se/books?id=LA9QDwAAQBAJ&pg=PT201&lpg=P...
Is eating 2 sandwiches also faster than eating one?
Are 2 electrical impulses also faster than 1?
I think not.