Is it better to eat ground turkey or lean ground beef?

No clear winner. Read the label- these are essentially equivalent if the fat content is similar. Both are good sources of protein, and the differences in types of fat are negligible between them. As always, vegetable and some fish sources of protein are even more healthful, but neither ground turkey nor lean ground beef is a bad choice for meat eaters.
No red meat. Red meat should be avoided as much as possible. You can eat it occasionally if you really want to. Beef is the worst - avoid it - high fat & cholesterol. The protein you may get from it can be obtained from countless other sources such as beans, poultry, & fish. The iron you get from it is inconsequential. If you're still iron-deficient, take a supplement. Also lamb, goat, & bison are red meats.