We decided to stay at Nusa Lembongan during our visit to Nusa Islands. I´m not sure but I think most people choose to live there during their stay to these Islands, that was my feeling.
We really enjoyed our time at this Island, pretty small Island but still a lot of things to do and also big variety depending on where on the island you are. No matter what you look for, relaxation or party, budget or luxury, there´s for sure something here to match your needs!
My recommendation if you stay here is to rent a scooter/bike, it´s super cheap! It´s very easy to find your way around the island and you can drive over the "Yellow bridge" to visit Nusa Ceningan. Ceningan is the smallest of the three "Nusa Islands. But even f it´s small there are plenty of things to see. If you rent a bike and go there I recommend you to go to "The blue lagoon", and also just drive the main road along the water and you will find several beautifal places to stop by.
Another place I think you should go and see is Devils tear´s and Dreambeach, they are side by side and you find them on Nusa Lembongan.
And if you just want to swim or surf there are really nice beaches along Nusa Lembongan, and also really nice beachwalks during sunset, safe area to walk around even night time. The beaches here are really nice sand beaches, clean water and good bottom. I liked the beach here and on Gili Islands the best!