I think both have their pros/cons.
Nick takes forever to air new episodes, and the only show that I watch on Nick is iCarly.
Disney airs new episodes frequently and has a lot of shows running at once (Wizard's of Waverly Place, Good Luck Charlie, Shake It Up, etc.) unlike Nick where the three main shows are iCarly, Victorious, and Big Time Rush. The old Disney shows were a lot better, but I really like Suite Life on Deck, Wizard's of Waverly Place (this season isn't that good though), Good Luck Charlie, and Shake It Up is okay.
That's just my opinion. Agree or disagree? :)