I bought 4 different running bottoms this year. Three are from Nike: one traditional looking running shorts, with the difference being the liner is spandex and feels like bike shorts, not those mesh things I hate. I don't think traditional running shorts flatter me too much, but these are OK. They are not too short. Then I bought a pair of knee length shorts that are like tights, but have a wide waist band and are really flattering. They hit me just above the knee. Finally, I got a pair of running knickers that are grey and flared on the bottoms.
I have a black running skort from Athleta. It's very comfortable, but I wish it was a teeny bit longer (and I am short). And finally, somewhere in the bottom of a drawer I have 2 pairs of Nike gym shorts from my aerobics days. They are more like bike shorts, but shorter.