The Antarctic Peninsula is by far the most heavily visited part of Antarctica. As the piece that pokes the furthest north, it is also the area with most wildife, and also the place with the most human history and settlement. There are quite a number of different sites that ship can visit, although most of these sites serve a similar biological or cultural function.
Despite the common misconception, there is not a high diversity of wildlife here. On a typical trip, you should the three main penguin species. In fact, there is a bigger range of animals to be seen travelling along the Beagle Channel coming back into port! However, there is some good concentrations of seabirds, and many colonies.
There are a lot of ships that go to the Antarctic peninsula. This is the main money maker for many expedition ships. In fact, there are even some companies that only go here and the Arctic! Because of the large amount of visitors, there is an attempt to have the ships and sites rotate by an organization called IAATO. This works reasonably well, and for most days it will feel like you are the only ship. I visited the area with Silversea expeditions.