Well, I only have two towns I can really say I experienced, but I'll go for the less known one first.
Dragon Valley.
Changes to make in Edit Town: Dragon Valley is a blank slate. It doesn't auto place ANY lots. I love that. It has a TON of 64x64 lots so you can place the Backlot from Late Night, the large Equestrian Center from Pets AND that large Showtime Venue if you really want and STILL have room for your Sim to start a Dynasty. The only thing I can say I struggle with is the 20x30 lots, there are plenty but they're all facing the wrong way and I'm OCD.
Spouses: Dear goodness. Bradan MacGrath is a day away from completing his LTW. He's also considered very wealthy. There's also the O'Shea brothers, they can make for one, a great spouse, or two, a great populating device for the town. Sioban Murphy is gorgeous and I believe she's also artistic - well into music, but it can go either way. I adore the Sackholme siblings. There noses can be a bit small but I always try to include them in my files. The O'Connells are rich, the O'Reilys are gorgeous and I think fairly well-off. Aaron Finnigan makes pretty children and my personal favorite: Quinn Flannagan. I adore him. I just... he's just awesome. He's relatively high up in his career. He learns the logic skill very quickly (good for young again potions for your Life State's Dynasties) and I absolutely adore his genes. All beautiful children. Though he is a full fledged adult, you'll get plenty of time with him to make it count!
Ease of Movement: I love this town. It's easy to move and it's easy to locate things. Even when I use mods that would heavily bog down the town I experience little or no lag. The layout is easy to use and in general I find it incredibly pretty to use. I was able to complete my Life State's Dynasty after a long haul through there with minor issues. I did have crashing towards the end, but that was because another file got corrupted and I was in dire need of a Factory Reset.
Special Pros: Lots of big lots, free baby dragons everywhere (that sell for $1,000 after it's been hatched), a community garden to get your crops started, no already placed lots that you have to delete because they're where you want to be, there are very few combined buildings for anyone who still struggles to get those opps to roll... the list could go on. Not to mention it's a gorgeous town, it's got mountains and beautiful colors. It looks like fall all the time!
Special Cons: The Special seeds (for the most part) are found on top of those mountains. Talk about a run. When your Sims travel it will drop you off on the other side of the world (which takes a long time to recover from). There aren't any EA lots placed from the start (so if you really just wanted to get up and start, you would have to place lots first, I don't mind doing that, but like I said - OCD). Finally, any and all EA lots will seem out of place. I tend to try to use the Pets versions of Ambitions lots as they look a little better, but until you get your hands on them to upgrade and fix, those lots will likely look a lot out of place in this beautiful town.
**There's now children's books in the library originally. However I've messaged the Mods and they've said that with Dynasties it's ok to add the toddler bookshelf. If you do plan to do that though, I would double check with a mod!
Overall, I highly recommend it for ANY Dynasty. I struggle to run Isla Paradiso, Bridgeport and even a full Sunset Valley after a certain generation, but this town has never given me any problems, all the way to generation 7 of a Life States Dynasty. It's a beautiful town, I can SUPER recommend it for a Life States as if you wait long enough most of the townies will be turned and you can encourage a townie-only dynasty there. I also love the genetic build there. I really dislike the EA middle-slider face, so it's nice to have a lot of variety.
The other town I've played in is Sunset Valley, but I think everyone knows the pro-cons of that one, summed up in my opinion.
Sunset Valley.
Changes to make in Edit town: Sunset Valley is really a mess to me with all the lots that need to be placed. Honestly all the auto-placed lots drive me mad. I bulldoze every single one of them and have to replace everything. Not fun.
Spouses: Everyone knows the spouse choice of Sunset Valley, but to sum it up for others who haven't played long: Agnes. Agnes. Agnes. Agnes. CRUMPLEBOTTOM! If you're in Sunset Valley, she's likely your new best buddy. There's always Chris Steel, and what not, those are usually the go-tos for a Dynasty, but I encourage people to look at Leighton Sekemoto, Tori Kimura, Emma Hatch, Cyclone Sword, and Mortimer Goth (if you can wait for him to age up, he's quite a nice looking townie).
Ease of Movement: Sunset Valley USED to be good for my computer, but with all the expansions and everything, I'm worried I won't actually make it to the end of my Immortal Dynasty I've started there. The town feels cluttered - especially if you have all expansion packs. Not so much if you don't though. So, I'd weigh the options there.
Special Pros: Most people know this town like the back of their hand. There are no combined buildings, and the Immortal Dynasty was almost built with Sunset Valley in mind (as it was the first town and the town that everyone has).
Special Cons: There is all of 2 or 3 women pregnant at the start, so no children will likely spring up anywhere else. There is a lag that will come up after a few generations of playing (I've only had this with almost all expansions installed). And this may just be every town, but I feel like Sunset Valley's special seeds take a very long time to show up for you to hunt them down.
Sunset Valley is obviously a good town, it's the first town, so I can't complain too much about really knowing all the townies that live there. There's a full graveyard with plenty of options for a spouse if you're really running out of ideas and you've got a Witch ready. I would recommend it for any dynasty, just keep in mind that if you're staying there for all 8 generations to plan your expansion pack addage accordingly.
**Edited because I totally forgot about a piece in the library!