How much do people value having local stock compared to grey import stock (ie. what premium are you willing to pay for a local variant of a phone compared to a grey import variant of that same phone)? Also, what benefits do you really get out of having a local variant instead of a grey import? From what I've read so far, it's mainly the software included on the phone (which isn't a problem with grey imports if you can root the phone) and local warranty.
I'm looking at a Nexus 5 32 GB and the Google Play store sells it for $449 (I believe this one is local stock, but I'm not entirely sure; could someone confirm?). Kogan sells it for $429 (grey import).
It depends on the product and the importer. In this case I would definitely buy it from Google Play store.