In general, per Dorge (Firenock) and others, longer arrows are more accurate. And that makes sense. However, the accuracy advantage related to shooting a longer arrow could be negated by shooting a longer arrow that is less well suited to your bow or is a poorer arrow in terms of construction (spine, straightness, weight distribution along the length of the shaft, nock, and insert and point construction and straightness). In other words the accuracy improvement you would gain by shooting a longer arrow could be negated if the longer arrow is of poorer quality or a less perfect match for your bow. Quality of construction and materials is important.
A longer arrow is also usually heavier although at least one manufacturer (Firenock) makes arrows that reportedly overcome that issue. There are advantages and disadvantages to shooting lighter or heaver arrows including differences in trajectory and momentum carried down range.
I don't know anything specific about the arrows carbon express offers for your bow but all other things being equal the longer arrows should be a little more accurate (assuming they compatible in terms of minimum weight required and nock). That would apply both to hunting and target shooting.
If you plan to shoot the 20 inch for target practice and then switch over to the 22 inch for hunting, you point of impact will change. You'll probably have to re-adjust your scope. At the least, the 22 inch will shoot lower than the 20 incher.
Edited by jackpine, 30 May 2013 - 08:57 PM.