Close Combat is more powerful, but leaves you open as it lowers your defenses. Because you have Smack Down it sounds like you are ok with tackling Flying types, so Close Combat may not be great for that as your defenses will be lowered. A lot of flying types are Normal-Flying types tho, making them weak to fighting after Smack Down.
Brick Break is less powerful, but leaves you a lot less open then Close Combat. It would probably be better than Close Combat if you are planning on taking on Flying types.
I would say Brick Break is probably the better choice. Close Combat has less PP, and if, say you use Close Combat to sweep Sidney in the E4, then you won't have any more Close Combats. Brick Break is the best option.