Beef contains bunches of useful nutrients other than protein, including zinc, iron, and several B vitamins. I also have more control over fat content. My local grocery stores offer ground beef in a range of different fat contents: 23%, 18%, 15%, 12%, 9%, 7%, 5%, and 4% fat. I can also see roughly how fatty a steak is.
When cooking, beef stands up to bold, powerful spices, but doesn’t really NEED them. You can sprinkle it with salt, and it’s just fine. You can use a little pepper, and it’s fine. Or you can crust it with caramelised blackened herbs and cayenne pepper, and you can still taste the meat. (Well, as long as you can still feel your mouth, anyway.)
Besides, for those of us in or around farming areas, it’s easier to find independent organic beef farmers than it is to find independent organic chicken farmers. So if you’re fussy about the source of your meat, beef is easier to control.
I’ve heard that Beef has higher Creatine levels than other meats. Can’t remember where, though.
I do remember for sure that meat from free-range Bison had much lower fat and much higher Creatine levels than normal beef (surprise, surprise). It also tastes better than beef, and because of the low fat content you can eat large quantities of it without feeling overfull.