Brawl Mode: Fighting = In Brawl mode the point is to KO people and try and stay alive, well if you make the Cpu come to you you'll have the home field advantage so he'll most likely fall off the edge or get KOed trying to get you. Also you may want to watch your back if your camping in a 2-way field. Or if your in a indent in a wall or your back is blocked you almost have it won. Weaknesses though are if the computer gets a super smash ball you are in trouble. So if your camp you may want to have a powerful and a guy with lots of health like Bowser or Wario.
Adventure Mode = In adventure mode you know your constanlly moving so you can hide from the enemy easily. SO, preferlly you want a more speedy agility guy, like Sonic so its easier to dodge many enimies and still have a good attack. Weaknesses could be booses although if you know key hit spots it shouldn't be a much of a concern. Also, speedy guys are better in Brawl Mode are good for bigger stages.