I haven't stayed at Atrium, and own at Divi, so my perspective is based on that.
Divi has multiple buildings, some with about 6-8 units and others larger that are spread out across a peninsula of land that separates Little Bay and Great Bay. All the parking is in a central lot, so you walk through the landscaped grounds to your building, and almost every unit has a nice view of one of the two bays, although most aren't on the beach. The resort is set back off the road, with an secure entrance gate, so it's very quiet.
There are 3 pools located in different areas of the resort. It has a nice beach with some snorkeling along the rocky cliff on one site, and plenty of free chairs and umbrellas. Divi has a water sports building, where you can rent jet skis and other beach rides, etc. Another timeshare resort, Belair, is next door to Divi and shares the beach area, so you can walk there to a restaurant and small store. Divi has a small grocery and deli as well.
Since the buildings are spread out, including 2 that are on top of the hill at the end where the ruins of the fort are, it can be a longer walk to some buildings - and depending upon your kids that can be good or bad
Although the views from the top of the hill are great! When my kids were real young, it was kind of a pain to have to carry all the stuff back and forth from the beach for lunch, etc., but we also like the privacy and quiet of the layout. And a couple of the buildings are three story with no elevator. I know for some older people the layout is a negative, simply because of the walking involved. The resort runs a golf cart type shuttle along the path that goes from the front desk and parking area, up to the top of the hill, so you can get help with groceries and luggage, or just catch a ride if you don't feel like walking. If you don't see it going when you want a ride, you just stop by the front desk and the bellman will gladly take you. When we stay in one of the hilltop buildings, my daughter becomes friends with all the bellmen, she rides the cart so often!
We've been able to request some general areas, i.e., Great Bay side vs. Little Bay side, when we trade weeks as an owner; I don't know how flexible they are in honoring requests from people coming in via RCI.
The resort units have all been renovated within the last few years, so they are in good shape. Not fancy, but generally roomy and comfortable.
In comparison, Atrium is a high rise building - not sure how tall - maybe 8 floors. It sits right in the middle of a neighborhood of residential and commercial. It opens out on one side to a beach area. I've seen their beach but never spent any time there, and didn't have the impression it was one of the better beaches on the island. Often in SXM, one of the attractions is visiting all the different beaches, so I think many of the people staying there go to other beaches anyway. I don't know anything about their pool or the quality of their rooms, so someone else would have to comment on that. I expect if you're up a few levels, you probably have a good view out to the water view from the Atrium rooms.
The location of the two resorts is the other big difference. The Atrium is located close to lots of restaurants, some that you could walk to, although you have to be careful as pedestrians because there aren't good sidewalks in some areas. I know lots of people who enjoy going out and don't want to drive afterwards, love the convenience of the location. It's also close to a large grocery store. Divi has its pool bar and Gizmo beach bar, which are good for lunch and bar food dinners, but its fancier restaurant is pricey and doesn't compare to all the other good SXM restaurants. Belair has a casual restaurant that many people like and it's a fun walk down the beach. Otherwise, at Divi, you need to drive for dinners. Philipsburg is just outside the gate, and the Simpson Bay area, where Atrium is located, is about 5-10 minutes away. Since we've always taken our kids, we aren't big partiers at night, so driving to and from restaurants is never an issue for us. We routinely drive to restaurants in Simpson Bay, Maho and Marigot with no hesitation. We have gone across the island to Grand Case, the gourmet center, but that's a longer drive on windy roads in the dark, so that's less common for us. (But that's the same issue for both Divi and Atrium.) Another difference is that the traffic in the Simpson Bay area can be a pain, so getting in and out of the Atrium area can be very slow sometimes. That makes the drive to Orient Beach, one of our favorite destinations, faster from Divi.
I know there are people who consider Divi out of the way, and would only want to stay in timeshares in Simpson Bay or Maho areas. They love having all the bars and restaurants close by, and go to beaches on other parts of the island to spend their days. To me, staying in those areas is too much like being in a crowded city area anywhere - not on a tropical island - so they aren't attractive to me. But they are popular areas, so many must like their appeal!
You asked about parking. We've never had an issue parking at the beaches we go to - like Orient, Mullet or Friars. (The usual SXM warning: NEVER leave anything in your car, anywhere, even if locked.) Parking by some of the Simpson Bar area restaurants can be a bit crowded, but usually there's a spot to be found somewhere in the area, although you might have to cross the busy street or walk through the gravel parking areas (no good sidwalks there.) A couple of the restaurants we go to in Philipsburg have private parking lots, which will validate if you have a meal. Otherwise, parking in Philipsburg during the day can be challenging, and there are tow trucks that making a living towing people, even from spots that appear to be legal! There is one paid parking lot a couple of blocks off from the main street that we use, or we park in the Greenhouse restaurant lot and walk down the boardwalk to the shopping area.
As you can tell, we love SXM, so always glad to answer questions about it.
