LMAO, they're pretty much the same if you ignore the point meter.
Not really... in a Gym Battle you won't see Ash or the Leader thinking about making their attacks look good and things like that
It's a different style of battle, but it still a battle so it's still ridiculous to say Contest Battles aren't "real battles"... should I remind people of May VS Drew in Kanto GF ? some of the regular Contests also had nice battles...