Generally, we prefer NCL (but we are platinum on CCL, so obviously we don't have a problem with them). NCL's freestyle just suits us better.
I find the food comparable and the service is fine on both lines. While the cabins may be larger on CCL (although to me it's not enough to matter) I don't find the cabins as nicely appointed as NCLs ships.
And all things being equal - the dancing waiters is something I despise, so it is the deciding factor for me.
Like Snoozeman, I enjoy sailing out of Galveston or Houston in the past, and sorely miss NCL having a ship from that location.