You can't go wrong with Boulders or Ebony; they are equals, although I personally prefer the design and decor of Boulders.

We stayed at Lebombo in 2015 (haven't yet tried out Sweni.) As great as the food was at Boulders, it was absolutely spectacular at Lebombo. Major drawback with Lebombo has to do with aspects of the room layout and functionality. It's definitely stylish, but function definitely follows form to the extent that some of it was really frustrating (I believe I called them out in my TripAdvisor review.) While the rooms at Lebombo can't be considered "small", they are not as massive as the ones that are found at Boulders/Ebony.

If you have time for only one location, then it's Sabi Sands, hands down. Prettier landscape, feels more "wild" (although it still pales in comparison to places like the Okavango and South Luangwa), and slightly better game viewing - it's often referred to as the Leopard capital of S. Africa.

RM is also uber luxurious, but is in a smaller area and it's completely fenced in... more reminiscent of an animal park than a true game reserve.

We're going to Tswalu later this month (combining with South Luangwa and Lower Zambezi N.P. in Zambia.) For first-time safari-goers that want a "big 5" experience, it shouldn't be someone's first (or even second or third) choice. Tswalu is (supposedly) a much more subtle experience. While there are some big predators at Tswalu, a big focus is on the smaller (and often nocturnal) species such as Meerkats, Aardvark, Aardwolf and Pangolin. And simply enjoying the stunning scenery of the Kalahari.

Regardless of your choice, you'll definitely have a wonderful time!