I really like c-rigging with all other structure and cover being equal. Main reason I like carolina is that you can cover lots of water and I feel that the carolina rig gives the plastic a more real effect being that its free floating behind the weight. With T-rig you kind of have to fish it slow from my experience atleast if you fish it fast with the weight being so close it restricts the bait and I've never had much experience with it fishing t-rig fast.
Example of this was when I fished in a tourney few weeks back I was throwing a c-rig into grass and dragging it really slow on the bottom. At first I wasn't getting any bites, but then on one cast I could feel my weight being hung up. When I loosened it from the grass instead of letting it hit the bottom right away I dragged the weight through the water probably a foot off the bottom, then I got my first bite. So rest of the tourney I would throw the bait and work that carolina rig real fast so the weight would barely touch the bottom and I had great success.