11.537
Really, there is no answer to your question.
What LED?
What photo transistor?
What transistor amplifier?
What do you mean by "detect"?
What ambient light level?
What nearby reflecting surfaces?
etc..
etc ...
And how do you suppose a camera would be better?
Even if the photo-transistors could respond to light from the LED would there be sufficient difference to allow you to use the difference to control direction?
How accurately do you want the direction to be controlled, +/- how many degrees?
I don't think your project is at all simple and you will probably need a lot of experimentation which may ultimately fail.
...R