Our family is going on our first cruise with RC on the Anthem in April! We were debating the same question and ultimately chose a beach bed on Chill Island because it was closer to the Chill Grill and and some of the other places. Videos I've seen say that South Beach is senere, etc. which has its own advantages, but we didn't want to be so far removed from all of the action (we're probably not going to do the water park). I also found out that Majesty will be docked there before us on the same day, and I didn't know how crowded it will be (though all of the videos and reviews say that chairs and loungers are plentiful), so just in case, we booked the bed because we liked the thought of having a place to park your stuff for the day. Enjoy your trip!
Update: I found where someone posted a cabana guide map of the day beds and cabanas and their numbered locations. It looks like the South Beach day beds are closest to the Chill Grill (I was wrong about what I said earlier about the Chill Island beds being closer to it, oh well). I tried to cancel the Chill Island beds and make one for the South Beach one but both are sold out, so I'm staying with what I have. Here's the link: https://boards.cruisecritic.com/topic/2722616-mariner-live-review-4nt-bahamas-jan-6-10th/page/3/
