If you google for "best expansions pack + sims 3" you'll find out that Late Night was by far the most popular ep among simmers (I think LGR has it ranked also very high on his list).
source: http://www.thetoptens.com/best-sims-3-expansion-packs/
And this says it all.
Let's give it a try: Late Night's best feature was Bridgeport (in fact, it was my second favorite world, so they did a pretty good job with it). The problem: If you don't use a fan-made patch the map suffers of significant routing errors that eventually can corrupt your save file if you don't use mods such as errortrap etc.
Then we had apartments (camera-movement of doom, rabbithole neighbors, NO (!) new gameplay at all, ZERO control over neighbors etc.) and with them came elevators --> always leading to a traffic jam inside the building + more routing errors + sims getting stuck).
In addition we got pubs, night-clubs and vip-lounges - everything neat in theory, but since they were almost always empty it seemed like a useless (because dysfunctional) addition to me.
Also a very poorly designed celebrity system that made everybody become famous only because they talked several times to a VIP sim (resulting in a town full of VIPs), paparazzis that always leave as soon as you start interacting with them (which is so dumb) etc.
And - of course - vampires, however, they got reworked later anyway. Nuff said.
The only addition I truly enjoyed were butlers. They were alcoholics (drinking at the bar all day long) and it was great (but for real the AI was just terribe --> you can google it yourself "Sims 3 + butler + alcoholic)!
And those were the *Special* fetures of Late Night (don't forget, every Sims 3 ep is packed with set dressing --> rabbithole interactions). I am sorry, I just don't see any more depth or better gameplay features in those eps in comparison to TS4. On the contrary.
Almost everything in TS3 was half-baked at best.
Conclusion: If you love the numbers game (meaning: quantitiy over quality) stick with TS3.
By the way: Let's better not start a discussion about the glorified stuff pack (called Generations)...
--> http://www.metacritic.com/game/pc/the-sims-3-generations
