Koh Rong or Koh Rong Sanloem — which should you choose?
Koh Rong gives you more variety and more freedom once you arrive, from lively Koh Touch to calmer Long Set and quieter beaches farther west. Koh Rong Sanloem is smaller, quieter and better suited to travellers who are happy to settle into one area for a few days. The better island depends less on the name and more on how much choice, movement and nightlife you want around you.
Answer
The old rule that Koh Rong is for partying and Koh Rong Sanloem is for peace is no longer very useful. Koh Rong has more variety. Koh Touch is still the main nightlife area, but Long Set is much calmer and Sok San quieter again. Roads and taxis make it easier to move around, so you have more options if you want to try another beach, restaurant or part of the island. Koh Rong Sanloem is smaller and slower. Saracen Bay is the easiest place to stay, with a long beach, ferry access and enough restaurants for a few relaxed days. M’Pai Bay has more village life and a more social feel. Lazy Beach and Sunset Beach are quieter, but getting there takes more effort and there is less around once you arrive. For families, I would focus on the beach rather than the island name. Saracen Bay works well if you want an easy, quiet stay and do not plan to move around much. Long Set is a better fit if you still want calm but like having more choice nearby. I would avoid Koh Touch if late-night noise is likely to be an issue. One night is too rushed for either island. Two nights works, but three is better. If you only have a few nights, stay on one island rather than spending part of the trip moving hotels and catching another ferry. Ferry schedules and pier stops can change, especially when the weather is rough, so check the details close to travel and leave some breathing room before an important onward connection.