They are both healthy food choices compared to most meats, and there is no major reason to prefer one over the other. However, there are certain differences. Overall turkey has fewer calories than chicken and is lower in fat, especially the breast meat. This doesn't apply to the liver, though, so it depends on which parts you like to eat. Also, turkey has more protein than turkey, so you could find you are eating more turkey to get the same nutritional benefit.

For more exact information, you can use a tool like this nutrition date site. Some facts about turkey are shown on this page; to compare the two meats, just type 'chicken' in the 'food name' box on the top right.

Another thing to consider is the quality of the bird itself. Free range poultry is generally more healthy than factory farmed, and chicken is often easier to find than turkey if you are looking for an animal welfare product - something else to bear in mind when choosing.