Yeah, even though the Raccoons is possibly my favourite series, I have to agree with everyone else. Mr. Burns is way more evil. They deliberately made Cyril Sneer less evil, gradually, starting more or less in the second season of the Raccoons. The only time he's ever really been comparable to Mr. Burns (although the basic personality was always very similar) is in the original specials, particularly the Lost Star one where he kidnapped everyone and planned to blow up the mountain with everyone inside as he left. Even then, I gotta go with Burns. Later on he was pretty grumpy, stingy and often inconsiderate, but not really evil. The episodes started to look elsewhere for their villains, such as Cyril's business rivals. Cyril was occasionally even portrayed as the good guy later on.
If it were a question of "who's your favourite villain out of the two" it would be a tougher answer, but Burns is definitely more evil.