If your kitchen is large enough, then having a kitchen island installed gives you the advantage of having an extra kitchen working area. Also the islands can be built with cabinets which can match the rest of the kitchen. The cabinets then can be used for the storage of pots and pans and countertop appliances. In addition, you can have the island customized for your individual needs. So maybe you’d like a wine cooler or a small refrigerator for cold drinks worked into the design. Too an island can be used only for meal prep and cooking so that a small prep sink can be installed in it as well as a cutting board.
However; in a smaller kitchen an island may not be practical because of space limitations. It could interfere with walking around the kitchen or opening the refrigerator or kitchen cabinet doors. In this instance, you may consider a rolling island which can be used and then rolled away and stored.
But, what if you have an extremely large kitchen and both you and someone else in your household like to cook at the same time. Then you may want to look into having a double island installed in your kitchen. Also when you have a double island custom installed, it gives you more work space and places for you and your company to sit. Too with two self-styled chefs sharing a kitchen, then having enough storage space is very important. But a double island can give you needed storage space on both sides of the island. Here then definitely having this custom made may be the best solution. You may want a sink at the one end additionally so that there is a handy water source; plus, room along the whole counter for food preperation.
A second island also could also work for just one cook. One island could be used as the prep and cook area, and the other island could be where people sit. Some cooks enjoy having an audience when they cook too, but actually not in the cooking space; this then could work very well.
Having an island in your kitchen; and the type of island, is a matter of space, personal choice and needs.