Which EP next?

[Paperbladder]

University is probably the most boring expansion, but it does add those want slots for the "Upgrade Pre-Uni Sim" options.  Unless you're sending a CAS retard there, there's not really that much to do.  It also seems like a cheat since an unpatched game gets you to L9 of a standard career track.

Nightlife added Cars, and this gives your sims a level of "freedom" that they didn't have before.  Instead of waiting an hour for the Taxi, your sim could just jump into the car and drive anywhere they wanted.  I scoffed at the feature at first but EA actually implemented it well.  Oh, and Vampires.

I actually liked OFB more than other people did.  It allowed you to make a scenario where a slacker could quit his job, whore out his house, and still make some money.  That, and you could hire personal servants.  As for the actual "Sell stuff" part, I found it too be too easy much like the following expansions.

I would actually recommend that you just play TS1's Unleashed if you want pets.  The pets are much too easy to train compared to the predessor and there are no incentives to do so.  A gold ribbon'd pet offspring fetches $3000, I don't know if Pets does that.  I pretty much got through 85% of the features in a day, the only things that I didn't do were Werewolves and Breeding.  Heck, the dogs in Pets don't even fetch you the paper like in Unleashed.

I didn't try Seasons all that much, but it adds the most to the game engine.  To me, it seems like they broke up TS1's Unleashed into two expansions since first we got the mediocre Pets expansion and then Seasons which actually affects standard play.  I didn't play through it all that much so I haven't seen a Sim overheat but I wouldn't want to go without it if I decided to play again.  Of course, parts of this expansion were supposed to come with the sequel...

[Zazazu]

I love (some) of the new build mode features, and I still want my build mode stuffit pack!

Please please please! Curved walls, more versatile roofing, pillars that actually meet up properly with the floor above....a non-cheaty way to make nice modular stairs.

[akatonbo]

Which EP to get really depends on what you enjoy most about the game, but I'll second the statement that, unless you REALLY REALLY want your Sims to have Pets, your next EP should be Uni or Seasons. Pets is very focused on Pet things, with little else included; Uni is FULL of goodies, and Seasons comes with even more new jobs than Uni (I love new jobs), although Uni wins bigtime in the career reward department (at least, if you like the idea of the cow plant and the resurrection device).

[Tigerlilley]

I like Uni as well
But i vote for Seasons

[J. M. Pescado]

Which EP to get really depends on what you enjoy most about the game, but I'll second the statement that, unless you REALLY REALLY want your Sims to have Pets, your next EP should be Uni or Seasons. Pets is very focused on Pet things, with little else included; Uni is FULL of goodies, and Seasons comes with even more new jobs than Uni (I love new jobs), although Uni wins bigtime in the career reward department (at least, if you like the idea of the cow plant and the resurrection device).

Items alone cannot really be a major consideration, since it's trivial to reenable the item in a newer expansion. The real selling point of Uni is how it gives you 6 want slots, which is basically a Must Have with all the want spam plaguing sims with each added expansion. Not sure if Upgrade Pre-Uni works correctly without actual Uni. Otherwise, it's not-so-great, as the Uni experience itself is bland at best and its installation permanently costs teens a want slot. But nothing stops you from acquiring them all...

[akatonbo]

Items alone cannot really be a major consideration, since it's trivial to reenable the item in a newer expansion.

Is it, now?

[J. M. Pescado]

Yes. You need a simple OBJD hack to disable the "cripple" behavior, then dump out the missing animations, meshes, and textures verbatim, and voila, object reenabled.

[Gwill]

I assume that only works for basic objects like beds and chairs, not compliceted stuff like pool tables and musical instruments.

[Arina]

I think the awnings and storybook build set came with Pets and I really like those. But Seasons is the best - it has kitchen decorations, leftovers, and really nice lighting effects. That's the main thing I'd miss - even without actual weather, summer looks sunny and autumn looks... autumn-y. It adds more variety. It's one of those things that's so subtle it's not really gonna be mentioned much but, to me, the lighting is what makes Seasons. And obviously there's loads of other things about it but they've all been mentioned in this thread already.

[Gwill]

Awnings definitely came with OFB.

[Lorelei]

You seem to have decided on Seasons, and I applaud that.

I got all of the EPs at once, and that may have prevented me having hack and BodyShop issues with Pets, and I was slightly leery of adding a new EP to the batch, having unfond memories of EA borkennesses, but Seasons is remarkably stable.

I will share that I experienced some Plant Sim issues when trying to run a comm lot business, so it may be wise not to have a Plant Sim try to work off-lot, or it may just be me having another "only I have it" bugs. YMMV.

I liked Uni, but mostly for the YA age stage, extra want/fear slots and locks, and because hey, I'm in college again, so I find it amusing to recreate classmates as Sims and then let them run around unsupervised in Uni hoods.

I don't do much with Pets other than give two or three Sims a dog or cat. I could do without it, but I like having the animals around. If it was causing issues, I'd be less enthused. It's not as stable or useful as Seasons.

Cheers, have fun, whatever you pick.

[Count Four]

Seasons is installed, patched, all that good stuff. Right off the bat Rose Greenman got pregnant with twins. 
(I swear I have the super-top-secret OMGTWINZ!!!1! base game. Really. My sims were having twins left and right before I had so much as a single EP.  They still are. The first sim that ever got knocked up in my game had twins. So did her daughter. Cheesecake? It is to laugh, hahahahahaha-groan. ACR is fantastic, but what would come in really useful is a way to prohibit twin pregnancy by lot. It's all right for a brand new couple; if they get twins, they've pretty much got a complete family in one shot. But other families don't need two more. And yeah, I know, I can abort/use the morning after pill, but it wastes time.)

I've only had a few hours to play, but I like Seasons. New careers, gardening that actually has a point, selling goodies, OMGWEATHER!. The storm sounds are great, they keep freaking the hell out of my cat and dog.  The cat is fascinated with the sprinklers, too.
I like working on getting badges for them, so yay for the gardening badge.
And they're rolling wants now to buy craft benches; they've never done that before, even though I have OFB.

I've noticed with a plantsim in the house it's really easy to 'neglect' the regular sims. Since the plantsim never sleeps, I keep getting more focused on them than on the ones who become inactive every night.

But--are apple trees ever healthy? And why do the apples look grey on my trees? Other produce has color, but the apples look like zombie-fruit. They have color in the inventory, though.

[Kyna]

In spite of it's name, Twojeffs' Triplets and Quads hack sounds like what you're looking for.  In the full version you have the option to select how many kids are born, so you can select one child instead of twins.

To get a plant or tree to thriving you'll need to have a sim with a gold gardening badge talk to it.  I tend to put fruit trees inside a greenhouse so that they don't get affected by bugs, which helps to keep them healthier without the need for perfomance-affecting ladybug houses.  The apples probably look grey on the tree because the tree is sickly.