I am thinking about getting either FEPG 500 or 1000.

As far as I know there are just 2 major differences between the PG500 & 1000.  The 1000 is insulated and the 500 is not, and then how the "top" opens - either by the two front doors for PG500 or the whole flip-up hood for the PG1000.  There are the "looks/design" differences between the two.   I bought the PG500 (3-1/2 years ago and still love it) rather than the PG1000 because I liked the looks of the 500 better and it cost less.  I live in Western Washington and when it rains I use my grille under a covered area so I can't speak as to how it works when exposed to direct rains.  Since there are electronics and pellets involved in this unit, I would contact Cookshack to ask about effects of direct & prolonged exposure to rains or snow.  Mine has gotten rained on a few times when cooking without any ill effects.  Cookshack does offer weather covers for these units when not in use.  I think the uninsulated 500 would burn a few more pellets per hour than the 1000 during real cold temps, but think the 500 does not dump quite as much heat with just a front door open (when checking food) as the 1000 would with the hood raised.  I bought the front shelf with my PG500 and would highly recommend it as it nice to have that space in front of the doors.  The doors/front of the PG500 are slightly angled so when its doors are opened they do so at a slight upward angle and thus do not knock small not-so-high items off the shelf (such as a tray, spatula, tongs, etc).  I would buy whichever unit you think looks the best and fits your price range.  FEPG grilles are great units that produce amazing food - you will love it. Changing pellets in hopper of PG500 is easy - just find a pliable bucket or a box that fits the space and then open the pellet dump door.  I would find a big colander to sift out sawdust from pellets near bottom of bags before adding pellets to hopper.  A small shop vac is also handy for cleaning out fire pot before your next cooks - not necessary after every cook (in my opinion) but do it regularly to avoid ash build-up in pot.  Just make SURE fire is completely out before doing so !!  Hope this helps.