Nikiti is a quite place overall, with places to choose from regardint eating and having a drink or two! It does have beautiful beaches around which you'll surely enjoy. Vourvourou is smaller, with fewer I think options, but a very beautiful place, and really natural. Try to avoid the central places. You can check out Sithonia attractions. Neos Marmaras is a busy little town, however there are many beautiful places to reserve, outside of the village and the good thing about Neos Marmaras, is the more options that you can find. However, there is also Parthenonas village, which is a traditional settlement 5km away from the crowds of Neos Marmaras. Beautiful view from up there, and scenic place. Nice accommodation in the area. It offers good local food, you're away from the crowds, but still a ten minutes drive from some really beautiful beaches.