When I was at CN in March the resort was dead by 10ish. We did manage to whoop it up with another couple til 3am one night. But that was us making our own party. We will be at CSA in Aug/Sept and we'll see if we're making our own party there as well.
We just returned from CTI and we found things winding down there around 10ish. Sorry this isn't helping you make your decision. We have been to CN 5 times and have always partied till all times in the morning in the Piano Bar. Some nights of the week they turn it in to more of a disco....lots of drinking and dancing. From reading the message boards...A LOT....it seems like it really just depends on the week you are at the resort. If all the couples there want to party, that is what you will get, and if all the couples want to go to bed early....you will need to make your own fun!
The nightlife is really what you make it. We've been to both CN and CTI and at times, they've both been dead and at others we've shut down the piano bar at 4am. The entertainment is there, you just have to find it!