An instructor helps a lot when learning to fly. Sims are a lot different than flying a real airplane. They are a lot easier to land and take off.

Instructors are there to make it so you don't crash.....and to help you learn to be a good pilot.

A lot of people learn w/o an instructor, but they usually crash a few times before they are succesful.

I would say that having an instructor is a definite plus.

Have fun and good luck.