Carnage is practically Venom but better in everything except intelligence.
Eddie Brock is smarter. I'm not saying he is in the level like Dr.Doom, Tony Stark or Reed Richards, but he is deffinitely not DUMB like some people on these boards seem to think. Brock was a well respected investigative journalist in the Bugle which makes him a decent deductive thinker, and he is half the reason that Spider-Man's team in Maximum Carnage won out in the end without any heavy hitters. He is also quite good at setting traps, he surprised Spidey more than once (Amazing Spider-Man #346, for example).
But on the main subject, Carnage with cosmic powers wins.