DN was awesome in the day. (Kim Possible, American Dragon, Even Stevens) Lizzy McGuire, Recess, Brany and Mr. Whiskers, sometime Suite Life of Z & C/Some episodes of On Deck, That's so Raven, etc...)
CN was 10/10 amazing in the day. (Batman TAS/NAS, Batman Beyond, Justice League, JLU, Teen Titans, old school Ben 10, Static Shock, etc...)
Disney is shit now.
CN has went down alot, but GLTAS, Young Justice are amazing. Adult Swim has American Dad, Family Guy, and Robot Chicken, all nice.
Overall: Back in the day and even now, CN is my favorite out of the two.
Nick is also a great choice. It has/had SpongeBob, Drake and Josh, Timmy Turner, BTR, Victorious, Zoey 101, Ned's Declassified, Jimmy Neutron, etc...