Stretch goals aren't KS exclusive. If your FLGS will be getting War, it'd definitely be cheaper to get it there.
Well, it depends. For Devastation, it was *really* hard to get it at all, at least in Germany. There was nothing short of ordering (for much higher shipping costs) Devastation Extended (and paying customs fees as well *grml*). Plus, what between the dollar and the euro, I think e.g. Fighter Plus is *definitely* a good deal -- even considering shipping. However, I share the feelin of: Look at how much of the money I'm spending is not even reaching the makers of this game or at least people in a store that I want to support.
So, really, the question boils down to: Do you have a shop that will definitely sell War? If not, I guess, the KS is where you want to go!