IMHO there is only one Aikido. Tell him that it is the manner in which they are taught that makes the difference. Some concentrates on variations, some on basics. Others on flowing, others on static. Others on self-defense, others for exercise, etc., etc. Depending on your affiliation, the method of teaching and focus on training varies.
Many Aikido Techniques can be executed without Aiki. Do you still call them Aikido?? Most Tai Chi moves use Aiki. Can we call Tai Chi a kind of Aikido??