1. Advantages: Every cell is specialized to do their own thing so: 1. They can focus on fewer tasks at once and do the work more efficiently 2. As all of the tasks require a certain amount of resources and energy to prepare, specialized cells save energy as they are always prepared 3. As they do one (or few) things all the time, they evolve faster in that particular task.
2. Animal cells do have a little more variety because plant cells have rigid cell walls. This limits the shapes that they can have. Both plant cells and animal cells have flexible membranes, but these are inside walls in plant cells, sort of like a trash bag in a trash can. Animal cells just have the membrane.