steel or aluminum rear sprocket

I am going to be replacing the sprockets and chain on my 750twin. Is there a real compelling reason to put on an aluminum rear sprocket? Obviously there is a weight savings, but would there be any real benefit? Would there be any real reason to stay away from an aluminum sproket because a steel sproket would last longer?

Your last sentence says it all, sprocket life will suffer with an aluminum sprocket.
I had to use an aluminum sprocket on my 79 twin because it had aftermarket Morris mags on it and absolutely no one made a steel sprocket that would fit, so I ordered a custom aluminum sprocket from Sprocket Specialist.

Steel; did you have it coated are what ever it is that they do to make it last better?

No, although if I buy another one I will