We liked Apgar for its convenience in being able to get into Apgar Village on our bikes for ranger talks, ice cream at night, the shuttle transit center, etc. Was nice to leave the SMB parked and easily ride our bikes places. There's even a bike path that goes to West Glacier. It does seem to attract the bigger RVs, though, as the sites are arranged in such a way that you park parallel to the campground loop roads, making it easier for trailers and whatnot. See the attached photo below. Kind of like just parking on the shoulder of a road, rather than pulling into a site that is perpendicular to the road. Also, if you are on the left side of the loop, your side doors will open toward the road rather than the campsite, unless you turn your van around (against traffic). Maybe other loops were different, I didn't notice. Not the most private of sites, but we weren't there much anyway. It's also one of the only CGs that can be reserved, but we got a site for two nights just by showing up.
The other campgrounds on the west side of Going to the Sun Hwy are very nice, and more private. But they don't really have much around them as far as facilities go. Our 8-year-old son was with us, so having ranger activities, ready access to huckleberry ice cream, the ability to swim in Lake McDonald (see pic), etc., was a plus at Apgar
Sprague Creek is a small, private-feeling CG right on the lake, but it fills up quickly. I did see another SMB camped there when we were driving through looking for a site, but nobody was "home" to talk to. Avalanche CG has some nice hiking nearby. I've stayed there in the past and it was a nice CG.