I would suggest 900 or 1100. And sites on the outside of the circle are my preference because they feel a little more spacious than interior sites.
Most Premium loops have the same amount of shade except for portions of 1400 IMO and 600 near the Meadow TP. If you liked 1500 (as I do) because it feels like a small, intimate loop with easy Comfort Station access, a bus stop, and near Meadow TP/pool, then 900 is my recommendation (our Premium loop when I choose to go Premium). It offers all those same things.
1100 interests me because sites are spaced well (again, on the outside I'm referring to).
You can put your requested loop on your reservation but keep in mind it's only a request and not a guarantee. To improve your chances of getting our loop, check in (on-line or in-person) as early in the day as you can. I like in-person but your travel plans dictate that point. When you arrive early, if you got your requested loop, great. If you didn't, you can go inside the check-in building and ask politely if a site is available in your desired loop. If someone is arriving the same day you are in your desired loop but hasn't checked in (on-line or in-person), the CM will bump them and generally give that spot to you and the other guest is none the wiser.
That's my two cents.
Bama Ed