Yeah, for me, this is the place where mid-lengths are a ton of fun. A good mid-length is way better than my little groveler in HH or OH mush. And better for getting around the lineup. I have one that is duck-diveable for me so I can manage it in the line up. So mid-size not a small longboard. The feeling of carving around on a mid-length on a solid wave is so fun. Reminds me of snowboarding, only better. Northern Shores is spot on, there's a plenty to learn in the mid-length thread that doesn't need to be rehashed.
For me it's...
5' 9" Lost Bottom Feeder in shoulder or less.
7' 2" CI Waterhog in head high+ mush
6' 2" Lost Quiver Killer in decent or better head high surf