I would use I look forward to seeing you. when the time to see them is not too far in the future. We have made a firm date to see each other soon.
I would use I am looking forward to seeing you. when the time to see them is farther into the future and no firm time has been set to see each other...we intend to see each other...hopefully it will happen.
However...this is just a personal preference. There is very little difference between the two sentences.
Student or Learner