Seems like there are pros and cons to most of them, but I think I'd isolate 8, 6 and 1/2 as the best spots. Here's why:
8 is right by the Potato Hollow spring but tucked around the corner and well off the trail. The views from camp aren't all that spectacular but walk a hundred yards and you're standing at a sheer 800-foot drop into Imlay. Very nice. Not packing tons of water to camp also very nice.
6-3 are all fairly similar in that they are up high on Horse Pasture Mesa with epic views. 6 is a little closer to the big edge and is quite a bit less walking from Potato Hollow spring than than 5-3 so it won't hurt so much to dry camp. Also nice to not be able to see your neighbors as 6 is tucked away by itself while 5-3 are within site of each other.
I didn't stop in and look at sites 1-2 but they are both very close to Cabin spring so that puts them on the list of desirable camps, IMO. The only bummer is that you have to get through so much of the trail that first day.
I'll be trying to score site 6 for my next West Rim trip later this year.
Imlay Canyon from near site 8:
The view near site 6 (very similar view a short walk from sites 5-3)
The view about 50 yards from Camp 4:
So I guess you really can't go wrong...
