When we were framing, we were >required< use 2" staples to shoot down
1/2" plywood deck. Having pulled enough of that stuff up, the 2" staples hold well, and the shorter you get, you get much less holding power. Besides, the cost between sizes when you get the larger sizes is nominal.
This assumes that you are using a narrow crown stapler, not a wide crown (roofing).
I always use the old shopworn formula that I learned years ago, and that is to pick a length of fastener that is approximately 3 times longer than the thickness of material you are fastening. So in this case, the plywood would be 1/2" thick, times three, or 1 1/2". Add back in the original material, and you have a fastener length of 2".
Remember the coating isn't always some kind of cool adhesive (check the country of origin) that sets up with the heat of application, but anymore it seems to be just a binder for the staples unless it is the tiny 18 ga. guys.
I would get the longest staples I could, with divergent chisel points, and when assembling shoot the staples so the crown was perpindicular to the grain, not parallel. You could use shorter staples with glue, but why take the time?
As always, YMMV.
Robert