Which town should I buy?

Sunlit Tides, no question about it for me. I have all the EA worlds and I think it's one of the best made...

Sunlit Tides is actually quite different from Isla Paradiso. The weather is tropical and it's island based in a different way, but most of us think of it as a different ocean (as in Pacific vs. Atlantic even though Sim Nation isn't really structured that way). The layout of the world is unique, and there's a volcano there, no resorts but you can place them. If you want something not so tropical for a change though, my favorite store world is Dragon Valley. Others are quite partial to Hidden Springs, Monte Vista, and Aurora Skies, etc. They each have some great things about them and come with (or are associated with) various forms of premium content. Perhaps you might look up some Let's Plays and reviews of the worlds you are considering so you can get more of a sense of what they feel like?

Lucky Palms is my favorite town that I own. I really like the desert theme, there are nice sims and most importantly there is a lot of room. I can easily fit all the lots I want from other expansions. I especially like how it has enough big lots. The town also has two sides a better town and rundown town, which can bring variety if you move to the other side.

I do like Sunlit Tides as well. It's not as spacious, but it's really pretty! The only thing I don't like that snow has kind of glitched appearence there, I think it's because of the water level or something like that? I know most people would probably not mind that snow doesn't look that good in a tropical world, but I prefer to have all of the seasons with all of their features in every world, regardless if that would be realistic or not.

While Sunset Valley reminds me of the California coast, Lucky Palms is inner California, with a smattering of Nevada strewn in for good measure. In the real world, you could just hop into your car and drive a few hours to get from one place to the other.

There are two threads regarding favorite worlds near the top in the "Worlds" subforum of the Store forum. You can see that pretty much all worlds have their fans, with a few notable exceptions (like Barnacle Bay).

Don't forget you can download Riverview from the store for free. I really like it for its small town / farm feel. When I play with horses I like to play there.

Of the 2 I like Lucky Palms more. I like playing on a house boat in Lucky Palms. Although I have Sunlit Tides I've never played there. I did use Traveler to vacation there for my sims to get married on a beach.

While Barnacle Bay won't be winning any popularity contests, overall it's not a bad world. It's more like a diamond in the rough, it does have it's own beauty just takes a bit of imagination and polish to make it shine. ;)

Between the choices of Sunlit Tides and Lucky Palms, I would recommend Lucky Palms for several reasons.
1 - It's a lot easier to navigate.
2 - The townies are very friendly characters to get to know.
3 - If collecting is your thing, there are plenty of meteor rock, gem and seeds to collect.
4 - If social play appeals to you, neighborhoods (as with door to door neighbors) are grouped 5 to 6 homes in close proximity of each other.
5 - There are plenty of empty lots to build on or add to.
6 - Plus, it comes with the wishing well which provides it's own bit of unique fun.
7 - Should you add the casino, it also is a fun lot.