I see, now you are making more sense for me to understand what your hoping to accomplish, with that said, here is my take on the difference your looking for. Please keep in mind I don't have a PG1000, but do have a FEC100 which has the double wall and 850* insulation, just like the PG1000.
I truly can see where they are coming from when they say the pellet consumption in the PG500 can vary as much as 1 lb of pellets. The settings that I use to smoke at 275* is the same as when I grill hamburgers at 300*, but in the middle of winter I have a hard time reaching that said set point(300*). I know I could raise the pellet feed rate to achieve this, but it's not a big deal to me. I would guess I'm using 1/3 more pellets in the winter months.
With all that said about the PG500 my FEC100, which is double walled and insulated, appears to me that it doesn't matter if I'm cooking in 20* temps or 90* summer temps. The insulation in these are that good.
I would guess that the pellet rate for 275*, which I use a lot in both, is almost 3 times as much for the grill over my FEC.
I buy pellets by the ton, so it really isn't a big deal, because the PG500 produces awesome food. I have a place in the garage to store them and at a ton I can get them for a little over 30 cents/lb.
I love my PG500, but at times in the winter I sure wish it was insulated. If I lived in a warm region like you do, I have no doubt that I would own the PG500 rather than the PG1000. Just my humble opinion, so take the advice for what you paid for it.
Ask up if you have any more questions and I'll do the best I can in answering them.