We've been to both locations.
We really loved the "King Size Adult Only" hot tub at KOA, and the fact that they have the entire pool area fenced off to block the wind, but use clear plexiglass sheets so you can still see all around the park.........no closed in feeling. The free popcorn is my favorite everytime the movies play!
We also went to Association Island back in July. Beautiful location, right on the shores of Lake Ontario.......with shoreline sites, everyone gets a window seat! Just a quick warning.......if you pick the "Windward Side" (sites L09 to L27) facing West out onto the lake, just keep an eye in case the winds pick up. They can come out of nowhere, and play havoc with your awning. The "Leeward Side" (sites H01 to H37) are much calmer, but doesn't offer the views of the sunset like the other side.
We have a 35 foot Georgetown motorhome and had no problems exiting the Interstate at exit 45 onto HWY 3 to HWY 178 and following the signs from there. All the pavement has been redone recently, and is a scenic approach to the campground. ENJOY