Luckily for us, I already counted every single piece when the stuff packs were released and noted those numbers down. So if you don’t believe me, here, the post with the exact numbers, counted and double-checked by myself, counting items that were available for multiple age groups only once, as is accepted standard for Sims 4 CAS item counts:

https://disqus.com/home/discussion/simsvip/lgr_reviews_the_sims_4_luxury_party_stuff/#comment-2038749531

As you can see, Luxury Party was in the same item count area as Diesel, whith ~55 items and Perfect Patio is in the same area as Outdoor Living with ~45 items. Both still topped Town Life with its ~40 items and are slightly beneath the Sims 3 average of ~65 items, which is strongly influenced by the fact that only two Stuff Packs actually included twice as many items as the current Sims 4 Stuff Packs, one of them being Sweet Treats which was sold for $30 instead of the usual $20 back then.

So, yeah, again, numbers don’t lie. And these numbers tell you exactly the same thing I told you in a much shorter version.

But as for the Sims 3 Store sets…
While true that the Sims 4 Stuff Packs are following the same style and release schedule, there is still a major difference: Price and content!
Sims 3 store sets were sold for about $20 each, including between 20 and 30 items.
Sims 4 Stuff Packs are sold for half the price, but so far delivered about twice as much content.

And all of that isn’t even taking into account the fact that every Sims 4 Stuff Pack so far came with 5 original simlish songs, recorded by real-life artists.

Also SIMVIP has review of every TS3 stuff pack here. Numbers do not lie. You can count them all.

TS4 stuff packs are half size compared to TS3 ones on average.

TS4 stuff packs are more like TS3 store sets than stuff packs.

I really recommend hot tub fans to get this pack. They are the best ever and the objects, overall, are very beautiful!