Affiliation gives a teacher and students a sense of family. But, you should probably make sure you pick the right family for you. Some things to consider are the costs. What the price is annually. How much a seminar with the head instructor ( or other high ranking instructor) will cost. (Since they are usually required annually) How much rank will cost your students, and you.
I just recently affiliated my dojo with the International Aikido Association, after looking for about a 6 months. I found an instructor whose philosophy was similar to mine. Sosa Sensei doesn't interfere with day to day operations and teaching. He just wants to improve our aikido and leave a great legacy of quality aikidoka.
Most importantly, I can learn so much from him! That is the exciting part of affiliation.
If you have any questions feel free to e-mail me.