Summit Lake is a small, swimmable lake with one campground on the north, and the other on the south. Technically I believe they are the same campground (with A and B loops in the North and C, D, and E in the south), but they're separate enough with different facilities and names that they really are two different experiences.

South side: Nice trees, nice camping spots. There's a whole loop (E I think) that is only for tents. South is $2 cheaper than the North side, most likely because the North has the flush toilets vs the pit toilets on the South. Which brings me to the two reasons I like the "other" (North) campground better:

First, the North side has flush toilets. Totally worth spending the extra $2 to go to the other spot if there's openings.

Secondly, the North side has a nice little beach/swimming area, whereas from the South side you run into a lot more swampy water weeds trying to get down to the swimmable parts of the water.

That said, if the North side is booked up or if you want something with perhaps a bit more room (depending on which site you find), the South side is nice, too. There's even a couple of very nice spots right on the lake. Either way, you'll do fine at either campground.