For me it is a tie between everyday clutter and little campers.
Every day clutter is great because it can add a few little details to feel as if a house is really lived in. I also like that a lot objects fit on small slots. Especially being able to put a radio on a small shelf without cheats like MOO is useful. The mirror that can be placed on surfaces while still being functional is amazing. As far as I know this is the first time a BB kit offers a possibility of placing objects that is not found in the base game or any other pack.
Little campers is great because it has a lot of functional objects, more than other kits. Other BB kits seem to be more about decoration than usable items. It is also great to get items like swings and don't wake the llama/yeti which were previously only available through EP for a small price. It is useful for people who don't have those packs (yet).
Decor to the max and pastel pop and first fits also have nice items.
It was nice to get desert lux for free. I have used the windows a few times but I don't think I would have bought it. The kits I mentioned previously are more interesting to me.
While some of the kits are OK, I still hope to see stuff packs return one day. I really miss them.