If you are just in the planning stages, it would make sense to make your reservation first, and then ask for loop suggestions.
From everything that I have seen, it looks like there will continue to be four levels of sites at the Fort: Premium, Preferred, Full and Partial. You state that you will reserve a Preferred site. That may be easier said than done. In checking for upcoming reservations for myself, I have found, more times than not, only certain levels of sites are offered. Preferred sites are hard to come by. That makes sense, as there are only three preferred loops.
The preferred loops are 100, 200 and 300. 100 and 200 are right next to each other and share an entrance/exit and comfort station. So, there is not much difference between these two loops, except the 100 loop is closer to the Settlement area. But both 100 and 200 are close to the marina, which is where you will catch the boat to the MK. The 300 loop is right next to 100 and 200, and is closer to the playground and dog park, but it is a pet loop, if that makes a difference to you.
The long-winded point I am trying to make is that the location of all of the preferred loops is pretty similar, so I wouldn't get worked up about trying to ask for a specific loop.
Have fun!
TCD
