It depends on your playstyle. Here's when I'd recommend each of them (I don't have MFPS but have all the rest).
Toddler Stuff is good if you do play them and want more bb/cas for them, they are a bit lacking for content without it. The playground items are great to add to parks, though are kinda big unless you have a large garden (aside from the slide which is a good size). Overall pretty decent.
Fitness Stuff, if you want a modern gym set. There is some nice stuff, it is basically what you would accept. Lots of athletic clothing, a lovely modern bathroom set that I really love, new gym stuff. If you already have Spa Day the gym stuff isn't much better/different though IMO. But it's good if you want modern fitness cas/bb. Rock climbing wall is nice, I rarely use it, it has to be placed over two storeys so can be problematic for that.
Laundry Day Stuff has a more rustic style to it, for cas & bb. I like that as I think we have not enough of it in TS4, but if that's not your style you won't like most of the pack. Good variety of cas, some of the bb objects are really great. Gameplay, it is what you would expect. Pretty involved with death from the dryer (by fire, not new type), can upgrade the machines, can use the line/tub if you like. Depends on if you want to play with laundry or not really, but good if you like that realism.
Moschino Stuff is better than I expected. I only got it recently so haven't played much with it, but I've been using the bb a surprisingly large amount. It's very modern, but the sofas and lights I really like, we needed the lights in this pack. Plus the windows are amazing! I've heard the career can be glitchy though, but it does offer lots of new poses for general photo taking and if you like to take group shots this really improves that. The cas is very personal, look up the items and see if you like them. A lot of them are very love/hate. There are a few more normal items that are nice, but it's what you'd expect for a high end fashion brand.
My First Pet Stuff I don't own, so can't comment on too much. Lots of the cas/bb look like they should have been in Cats and Dogs which annoys a lot of people, but doesn't stop them from being nice. The gameplay seems pretty solid with the new pets, though they are just four reskins of the same pet. New death type, which is pretty good for a stuff pack. Good for kids as they can study the pets, etc.. If you play families and want pets that won't take up household slots this is pretty good. If you don't own C&D I probably wouldn't recommend as there is a lot of items that you need C&D for them to function - new pet outfits, though I kinda hate them, plus new pet beds/toys/bowls/etc.. It's not most of the pack, but it's a fair amount, too much in my opinion.