Pros: amazing views, lots of hotels & restaurants. You get to see the sunrise AND the sunset.
Cons: you need to climp up the stairs first (but you get to drink from the fountain of youth on the way). No running water in the hotels. No interesting sights nearby.
Pros: Lake beach with pretty waves. Hippies. Running water. The Inca ruins are nearer.
Cons: no spectacular views of sunrise and sunset.
You can walk between the two villages (3 hours, with some spectacular views & Inca ruins on the way), or take the boat.
Yumani is the south village of the island. In the north there is another village called Challapampa. The boat stops at both. Most people disembark in the north, visit the ruins, then go hiking to the south, sleep there and take the morning boat back.
Fondest memory: There is really not much to do/see in Yumani, just a few restaurants and hostels...